WO2006107080A1

WO2006107080A1 - Vehicle suspension

Info

Publication number: WO2006107080A1
Application number: PCT/JP2006/307257
Authority: WO
Inventors: Hajime Satoh; Sachio Nakamura
Original assignee: The Yokohama Rubber Co., Ltd.
Priority date: 2005-03-31
Filing date: 2006-03-29
Publication date: 2006-10-12

Abstract

The suspension 100 includes first and second pneumatic spring devices 101 and 102. The first and the second pneumatic spring devices 101 and 102 include first air chambers 11 and 12 and second air chambers 21 and 22 inside of which a gas is confined to support a load. Moreover, the first and the second pneumatic spring devices 101 and 102 include first and second load carrying members 31 and 32 that are supported by the first air chambers 11 and 12 and the second air chambers 21 and 22 and whose effective load carrying area A1 of a part that makes contact with the first air chambers 11 and 12 is greater than an effective load carrying area A2 of part that makes contact with the second air chambers 21 and 22. The first air chamber 11 of the first pneumatic spring device 101 and the second air chamber 22 of the second pneumatic spring device 102 are connected via a first communicating passageway 51, and the second air chamber 21 of the first pneumatic spring device 101 and the first air chamber 12 of the second pneumatic spring device 102 are connected via a second communicating passageway 52.

Description

DESCRIPTION

VEHICLE SUSPENSION

TECHNICAL FIELD

The present invention relates to a vehicle suspension.

BACKGROUND ART

Vehicles such as passenger cars, buses, and trucks attain ride comfort by absorbing shocks from road surfaces by using suspensions. Moreover, while vehicles are running, suspensions attain driving stability of the vehicles by- reducing variation of a wheel alignment. A vehicle suspension includes a spring, a damper that damps the speed at which the spring expands and contracts, and a link mechanism that guides the movement of wheels in the up-and- down direction.

In general, a coil spring, a leaf spring, or a torsion bar is used as the spring. However, a pneumatic spring that utilizes a repulsive force generated by compressing a gas (such as, air) is also used (see, for example, Patent Document 1) . The pneumatic spring can maintain a vehicle at a fixed vehicle height by regulating an amount of gas (number of moles or mass) even when the number- of passengers in the vehicle or an amount of a load varies. In addition, it has an ability to vary a spring stiffness by varying the air pressure, air volume, or the like. [Patent Document 1] US Patent No. 4,200,270.

DISCLOSURE OF INVENTION

PROBLEM TO BE SOLVED BY THE PRESENT INVENTION

However, with the technique disclosed in Patent Document 1, it is difficult to differentiate the roll stiffness of the vehicle from the ride stiffness of the vehicle. An object of the present invention is to provide a suspension that can easily change the spring stiffness of pneumatic springs included by the suspension, so that the roll stiffness is substantially stiffer than the ride stiffness and also a pitch stiffness is substantially stiffer than the ride stiffness .

MEANS FOR SOLVING PROBLEM To solve the above problems and to achieve the goal, a suspension according to one aspect of the present invention includes a plurality of pneumatic spring devices that is attached to different positions of a vehicle to support a vehicle weight, each of which including a first air chamber that supports a load by a gas confined inside, and a second air chamber that supports the load with the first air chamber by a gas confined inside; a first communicating passageway that communicates, in a pair of the pneumatic spring devices, the first air chamber included in one pneumatic spring device with the second air chamber included in other pneumatic spring device; and a second communicating passageway that communicate the second air chamber included in the one pneumatic spring device with the first air chamber included in the other pneumatic spring device. An effective load carrying area of the second air chamber is smaller than that of the first air chamber. A volume change of the second air chamber is opposite from a volume change of the first air chamber, when a load is applied. The pneumatic spring devices stably support a load by the first air chamber and the second air chamber, and in the pair of pneumatic spring devices, the first communicating passageway and the second communicating passageway that communicate the first air chambers and the second air chambers with each other are included. As a result, the pair of pneumatic spring devices has, when these operate in opposite phase, a spring stiffness greater than that when these operate in the same phase. By providing such a pair of pneumatic spring devices in the left and right or in the front and rear of a vehicle, the spring stiffness of the pneumatic spring devices can be easily changed according to the running condition of the vehicle.

In the suspension according to the one aspect of the present invention, the pair of the pneumatic spring devices is attached to left and right of the vehicle.

In the suspension according to the one aspect of the present invention, the pair of pneumatic spring devices is attached to front and rear of the vehicle at a same side. In the suspension according to the one aspect of the present invention, the pair of pneumatic spring devices is attached to diagonal positions of the vehicle. In the suspension according to the one aspect of the present invention, at least one of a passageway switching unit and a throttle valve unit is provided between the first communicating passageway and the second communicating passageway . The suspension according to the one aspect of the present invention further includes a circulating passageway to connect the first air chamber and the second air chamber,

In the suspension according to the one aspect of the present invention, the communicating passageway includes a vibration damping unit that attenuates a vibration of the gas.

In the suspension according to the one aspect of the present invention, a stopper member made of rubber-like material (s) that generates a non-impulsive repulsive force when compressed toward an operating direction of the pneumatic spring device is provided in the first air chamber, at least on a side of attachment of the pneumatic spring device to the vehicle or a side of the load carrying member .

A suspension according to another aspect of the present invention includes a plurality of pneumatic spring devices that is attached to different positions of a vehicle to ease an impact from a wheel, each of which including a first air chamber in which a gas is confined, a second air chamber in which a gas is confined, being arranged opposite the first air chamber, and a load carrying member that is supported by the first air chamber and the second air chamber; and a communicating passageway that communicates the first air chamber with the second air chamber. An effective load carrying area of a part of the load carrying member, which makes contact with the first air chamber, is greater than an effective load carrying area of a part of the load carrying member, which makes contact with the second air chamber.

The suspension supports the load carrying members by the first air chambers and the second air chambers and includes the communicating passageways that communicate the first air chambers with the second air chambers. As a result, by, for example, intermitting the communicating passageways, the spring stiffness of the pneumatic spring devices can be easily changed according to the running condition of the vehicle. In the suspension according to the another aspect of the present invention, the communicating passageway includes a passageway switching unit that opens and closes the communicating passageway. In the suspension according to the another aspect of the present invention, the communicating passageway includes a vibration damping unit that attenuates a vibration of the gas . In the suspension according to the another aspect of the present invention, the second air chamber is arranged lower side than the first air chamber in a vertical direction. The load carrying member is sandwiched between the first air chamber and the second air chamber. The load carrying member includes a loading member that transmits the impact from the wheel to the load carrying member.

In the suspension according to the another aspect of the present invention, the first air chamber and the second air chamber are stored in a chassis. The loading member is penetrated through a through-hole provided in the chassis. In the suspension according to the another aspect of the present invention, a stopper member made of rubber-like material (s) that generates, a non—impulsive repulsive force when compressed toward an operating direction of the pneumatic spring device is provided in the first air chamber, at least on a side of attachment of the pneumatic spring device to the vehicle or a side of the load carrying member .

EFFECT OF THE PRESENT INVENTION

A suspension according to the present invention can easily change the spring stiffness of pneumatic spring devices included in the suspension according to the ^• running condition of a vehicle.

BRIEF DESCRIPTION OF DRAWINGS

Fig. IA is a schematic of a pneumatic spring device included in a suspension according to a first embodiment of the present invention;

Fig. IB is a schematic of another pneumatic spring device applicable to the suspension according to the first embodiment ; Fig. 1C is a schematic of still another pneumatic spring device applicable to the suspension according to the first embodiment;

Fig. 2A is a schematic for illustrating a pattern of piping that connects air chambers included in the pneumatic spring device according to the first embodiment via communicating passageways;

Fig. 2B is a plan view of the pattern of the piping shown in Fig. 2A, with the pneumatic spring devices according to the embodiment attached to a vehicle; Fig. 2C is a schematic for illustrating an example in which the communicating passageways are further provided for communicating air chambers to circulate a gas between the air chambers;

Fig. 3A is a schematic for illustrating a piping example where first and second air chambers included in the pneumatic spring devices according to a first modification of the present embodiment are all connected;

Fig. 3B is a schematic for illustrating a piping example that shows a condition in which, all air chambers included in the respective pneumatic spring devices are communicated in a pair of pneumatic spring devices;

Fig. 4 is a schematic for illustrating an example in which air chambers between the pneumatic spring devices according to a second modification of the present embodiment attached in front and rear of the vehicle are connected;

Fig. 5 is a schematic for illustrating an example in which, air chambers are connected between each pair of the pneumatic spring devices according to a third modification of the present embodiment located at diagonal positions;

Fig. 6A is a schematic for illustrating a piping example where a first air chamber and a second air chamber included in an identical pneumatic spring device according to a fourth modification of the present invention are connected;

Fig. 6B is a schematic for illustrating a condition in which the pneumatic spring devices according to the fourth modification are attached to front, rear, left, and right of the vehicle;

Fig. 7 is a schematic for illustrating an attaching structure when the pneumatic spring devices according to the first embodiment is applied to a double wishbone-type suspension;

Fig. 8 is a schematic for illustrating an attaching structure when the pneumatic spring devices according to the first embodiment is applied to a swing axle-type suspension; Fig. 9 is a schematic for illustrating an attaching structure when the pneumatic spring devices according to the first embodiment is applied to a strut-type suspension;

Figs. 1OA to 1OC are schematics for illustrating an example in which air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are connected to each other between different pneumatic spring devices, according to a second embodiment of the present invention; and

Fig. 11 is a schematic for illustrating a piping example in which air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are connected to each other between different pneumatic spring devices . EXPLANATIONS OF LETTERS OR NUMERALS

1, Ii , I₂, I₃, I₄, Ia, Ib First air chamber

2, 2i, 2₂, 2₃, 2₄, 2a, 2b Second air chamber 5c, 5d, 5e Communicating passageway

5ei First-chamber communicating passageway 5e₂ Second-chamber communicating passageway 8 Switching valve

10, 10a, 10b Pneumatic spring device 20 Vehicle

5₁ First communicating passageway

5₂ Second communicating passageway

8₁ First switching valve

8₂ Second switching valve 1Oi First pneumatic spring device

10₂ Second pneumatic spring device

10₃ Third pneumatic spring device

10₄ Fourth pneumatic spring device 13i First circulating passageway 13₂ Second circulating passageway

19 Stopper member made of rubber-like material (s) 100, 100a, 100b, 100c, lOOd Suspension

BEST MODE(S) FOR CARRYING OUT THE PRESENT INVENTION Exemplary embodiments of the present invention will be explained in detail below with reference to the accompanying drawings . However,, the present invention is not limited by the exemplary embodiments . Components in the following embodiments include ones easily conceived by persons skilled in the art or substantially identical ones. Although the present invention can be applied to suspensions of vehicles that run on road surfaces, such as passenger cars, trucks, and buses and vehicles that run on railroad tracks, such as railroad vehicles, the present invention is suitable particularly for the vehicles that run on road surfaces .

A suspension according to the present invention carries a load by first air chambers and the second air chambers, and includes a first communicating passageway and a second communicating passageway that communicate the first air chambers and the second air chambers, in a pair of pneumatic spring devices. Fig. IA is a schematic of a pneumatic spring device 10 included in a suspension 100 according to a first embodiment of the present invention. The suspension 100 according to the first embodiment is an air suspension utilizing an pneumatic spring to absorb and relieve shock from a road surface. The pneumatic spring device 10 includes a first air chamber 1 and a second air chamber 2 with a gas confined are arranged opposite each other, which are stored in a case (chassis) 11. According to the first embodiment, the first air chamber 1 is arranged at the side of a vehicle 20 being an attaching object of the pneumatic spring device 10. Therefore, the second air chamber 2 is to be arranged at a lower position in a vertical direction of the first air chamber 1, where the vertical direction means a direction of application of gravity, and the lower position means a lower side in ground height (direction of an arrow G in Fig. IA) . According to the first embodiment, the gas confined in the first air chamber 1 and the second air chamber 2 is air, however, the gas is not limited to the air. A load carrying member 3 is sandwiched between the first air chamber 1 and the second air chamber 2. A loading member 4 that penetrates through a through-hole 12 provided in the case 11 is attached to the load carrying member 3. An arm included in the suspension 100 and a hub that carries a tire-wheel assembly in a swingable manner are attached to the loading member 4. A force transmitted from a road surface to the vehicle 20 is transmitted to the first air chamber 1 and the second air chamber 2. Thus, in the pneumatic spring device 10, when a load is placed, a change in volume of the first air chamber 1 is opposite from a change in volume of the second air chamber 2. In other words, when the first air chamber 1 is reduced in volume, the second air changer is increased in volume. According to the first embodiment, the first air chamber 1 is communicated with the second air chamber 2 in an identical pneumatic spring device, or the first air chambers 1 and the second air chambers 2 are communicated with each other respectively between a pair of different pneumatic spring devices. Thereby, a gas pressure Pl in the first air chamber 1 is equalized with a gas pressure P2 in the second air chamber 2. Moreover, as shown in Fig. IA, an effective load carrying area Al of a part where the first air chamber 1 comes into contact with a first support portion CPi of the load carrying member 3 is greater than an effective load carrying area A2 of a part where the second air chamber 2 comes into contact with a second support portion CP₂ of the load carrying member 3 (A1>A2) . Namely, a pressure receiving area where the first air chamber 1 receives a pressure from the load carrying member 3 is greater than a pressure receiving area where the second air chamber 2 receives a pressure from the load carrying member 3. As a result, because a force Fl at which the first air chamber 1 pushes the load carrying member 3 is greater than a force F2 at which the second air chamber 2 pushes the load carrying member 3, a load transmitted from the loading member 4 to the load carrying member 3 can be supported by the pneumatic spring device 10. The ratio A1:A2 is appropriately about 2:1 to 10:1 (the same applies in the following) .

For the pneumatic spring device 10, the load carrying member 3 is sandwiched between the first air chamber 1 and the second air chamber 2 arranged opposite each other. And, the loading member 4 penetrated through the through-hole 12 is attached to the load carrying member 3 , and the loading member 4 shifts in the through-hole 12, whereby the pneumatic spring device 10 eases shock. In a conventional air spring, a point of application of a load has been located outside of the case. However, in the pneumatic spring device 10 according to the first embodiment, a point of application of a load from the loading member 4 can be set within the case 11 of the pneumatic spring device 10. As a result, the overall length of the pneumatic spring device 10 can be designed to be shorter than that of the conventional air spring. Consequently, the suspension 100 can be made compact . As shown in Fig. IA, for the pneumatic spring device^' 10, a stopper member 19 is attached, inside the pneumatic spring device 10, at a position opposed to the first support portion CPi of the load carrying member 3 on the side of attachment to a vehicle. The stopper member is provided inside the first air chamber 1 and on the side of attachment of the pneumatic spring device 10 to the vehicle 20 (namely, inside the first air chamber 1, on the side in a direction opposite the direction of application of gravity (direction of the arrow G in Fig. IA) ) . The stopper member 19 may be provided on the side of the first support portion CPi of the load carrying member 3 or may be provided on both the side of the first support portion CPi and inside the first air chamber 1 and on the side of attachment of the pneumatic spring device 10 to the vehicle 20. Namely, the stopper member 19 can be provided, within the case 11 of the pneumatic spring device 10, between the first support portion CPi of the load carrying member 3 and the vehicle 20. The stopper member 19 is made of an elastic material (s) and generates a non-impulsive repulsive force when being compressed toward an operating direction of the load carrying member 3 (namely, an operating direction of the pneumatic spring device 10) . For the stopper member 19, an rubber-like material (s) such as rubber or resin, which indicate easy deformation, allowing large deformation and returning to the original shape when exteernal force is removed, a helical spring, a disc spring, or the like can be used. The pneumatic spring device 10 can support the spring mass by the stopper member 19 even if the first air chamber 1 is deflated to make it impossible to support a spring mass by supporting the air pressure in the pneumatic spring device 10. Therefore, even if an air leak from the air chamber occurs, the stopper member 19 comes into direct contact with the first support portion CPi of the load carrying member 3 so that the mass of the vehicle 20 can be supported, the vehicle 20 can at least run at a low speed. As a result, even if an air leak from the air chamber occurs, the vehicle can reach a repair shop or the like by running at a low speed. Although a pneumatic spring device to be explained in the following also includes a stopper member, it is not always necessary to include a stopper member. Fig. IB is a schematic of another pneumatic spring device 10a applicable to the suspension 100 according to the first embodiment. Although the pneumatic spring device 10a has the same construction as that of the pneumatic spring device 10, a load carrying member 3a penetrates through a first air chamber Ia and a second air chamber 2a arranged opposite each other. The first support portion CPi of the load carrying member 3a comes into contact with the first air chamber Ia, which is on the opposite side from an opposed surface OP. In addition, the second support portion CP₂ of the load carrying member 3a comes into contact with the second air chamber 2a, which is on the opposite side from an opposed surface OP. The effective load carrying area Al of a contact part between the first support portion CPi and the first air chamber Ia is greater than the effective load carrying area A2 of a contact part between the second support portion CP₂ and the second air chamber 2a. The pneumatic spring device 10a indicates, when loaded with a load, a change in volume of the first air chamber Ia and a change in volume of the second air chamber 2a opposite from each other. Even the pneumatic spring device 10a having such a construction can be applied to the suspension 100 according to the embodiment.

Fig. 1C is a schematic of still another pneumatic spring device 10b applicable to the suspension 100 according to the first embodiment. The pneumatic spring device 10b is constructed so that an inner cylinder 3b reciprocates in an outer cylinder lib. A first air chamber Ib is provided in the outer cylinder lib. Moreover, a second air chamber 2b is provided in the inner cylinder 3b. The first support portion CPi of the inner cylinder 3b is in contact with the first air chamber Ib, and a load is transmitted thereto via the inner cylinder 3b. The inner cylinder 3b is protruded to the outside of the outer cylinder lib through through-holes Hi provided in the outer cylinder lib, and a load acts on this part. In the pneumatic spring device 10b as well, the stopper member 19 is attached, inside the pneumatic spring device 10b, at a position opposed to the first support portion CPi of the inner cylinder 3b on the side of attachment to a vehicle. Thereby the vehicle 20 is supported even when the air pressure in the air chamber has disappeared.

A load carrying portion 3C is provided in the outer cylinder lib, and the second support portion CP₂ of the load carrying portion 3C comes into contact with the second air chamber 2b. The effective load carrying area Al of a contact part between the first support portion CPi and the first air chamber Ib is greater than the effective load carrying area A2 of a contact part between the second support portion CP₂ and the second air chamber 2b. The pneumatic spring device 10b indicates, when loaded with a load, a change in volume of the first air chamber Ib and a change in volume of the second air chamber 2b opposite from each other. Even the pneumatic spring device 10b having such a construction can be applied to the suspension 100. Next, a pattern of piping that connects air chambers included in pneumatic spring devices according to the embodiment to each other will be explained. Although the pneumatic spring device 10 shown in Fig. IA is cited as an example to explain the piping pattern, the same applies to other pneumatic spring devices.

Fig. 2A is a schematic for illustrating a pattern of piping that connects air chambers included in the pneumatic spring device according to the first embodiment via communicating passageways. Fig. 2B is a plan view of the pattern of the piping shown in Fig. 2A, with the pneumatic spring devices according to the embodiment attached to a vehicle. The direction of an arrow L in Fig. 2B represents a traveling direction of the vehicle 20. Moreover, pneumatic spring devices 10χ to IO₄ are arranged at positions of a plan view as shown in Fig. 2B. However, for better visualization of the piping, the pneumatic spring devices that are to be arranged in the vertical direction are illustrated parallel to the page surface.

The suspension 100 shown in Fig. 2A shows a construction of a front part of the vehicle 20 shown in Fig. 2B . Because a suspension included in the vehicle 20 shown in Fig. 2B also has the same construction as that of the suspension 100 shown in Fig. 2A, a suspension in the front of the vehicle 20 will be explained in the following explanation. The suspension 100 according to the first embodiment includes the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ as a pair of pneumatic spring devices. The first pneumatic spring device 1Oi is provided on the right side with respect to the traveling direction (direction of the arrow L in Fig. 2B) of the vehicle 20, and the second pneumatic spring device 1O₂, on the left side with respect to the traveling direction of the vehicle 20. In such a manner, the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ as a pair are attached at different positions (in this example, left and right) of the vehicle 20, and the pneumatic spring devices ease an input from the road surface that wheels 21 receives. In the suspension 100, arms that guide a movement of the wheels 21 in the up-and- down direction are fixed and connected, as loading members 4i and 4₂ , to first and second load carrying members 3χ and 3₂, respectively. A first air chamber I_x of the first pneumatic spring device 1Oi and a second air chamber 2₂ of the second pneumatic spring device 1O₂ are communicated with each other via a first communicating passageway 5χ and integrated as a closed gas (first system Sl) . A second air chamber 2χ of the first pneumatic spring device 1O₁ and a first air chamber I₂ of the second pneumatic spring device 1O₂ are communicated with each other via a second communicating passageway 5₂ and integrated as a closed gas (second system S2) . In such a manner, the respective first air chambers and the respective second air chambers included in the different pneumatic spring devices are communicated with each other. Accordingly, when the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in opposite phase, the spring stiffness is higher (in this example, about twice) than that when the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in the same phase. Here, when the pneumatic spring devices operate in opposite phase means, for example, when the first load carrying member 3i of the first pneumatic spring device 1Oi shifts to a rising side (side of attachment to the vehicle 20, side of an arrow U) and the second load carrying member 3₂ of the second pneumatic spring device 1O₂ shifts to a falling side (side opposite from the side of attachment to the vehicle 20, side of an arrow D) . In addition, when the pneumatic spring devices operate in the same phase means, for example, when the first load carrying member 3i of the first pneumatic spring device 1O₁ and the second load ^• carrying member 3₂ of the second pneumatic spring device 1O₂ both shift to the rising side or falling side.

For example, when the first pneumatic spring device 1Oi falls in comparison with the first load carrying member 3i of the first pneumatic spring device 1O₁, the first air chamber I₁ of the first pneumatic spring device 1O₁ is reduced in volume, and the second air chamber 2i is increased in volume. Because the first air chamber Ii of the first pneumatic spring device 1Oi is communicated with the second air chamber 2₂ of the second pneumatic spring device IO₂, a gas pushed out from the first air chamber Ii of the first pneumatic spring device 1Oi due to a reduction in volume thereof attempts to shift to the second air chamber 2₂ of the second pneumatic spring device IO₂. In addition, because the second air chamber 2χ of the first pneumatic spring device 1Oi is communicated with the first air chamber I₂ of the second pneumatic spring device 1O₂, a gas attempts to flow in from the first air chamber I₂ of the second pneumatic spring device 1O₂ due to an increase in volume of the second air chamber 2χ of the first pneumatic spring device 1O_x. When the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in opposite phase based on the first load carrying member 3χ of the first pneumatic spring device 1Oi shifting to the rising side, the second load carrying member 3₂ of the second pneumatic spring device 1O₂ shifts to the falling side of the first air chamber I₂. Because the second air chamber 2₂ of the second pneumatic spring device 1O₂ is thereby reduced in volume, a gas is pushed out into the first air chamber Ii of the first pneumatic spring device 1Oi . In addition, because the first air chamber I₂ of the second pneumatic spring device 1O₂ is increased in volume, a gas is made to flow out of the second air chamber 2χ of the first pneumatic spring device 1Oi .

Such an operation of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ in opposite phase hinders the gas shifting between the first air chamber I_x of the first pneumatic spring device 1Oi and the second air chamber 2₂ of the second pneumatic spring device 1O₂ and a gas shifting between the second air chamber 2i of the first pneumatic spring device 1Oi and the first air chamber I₂ of the second pneumatic spring device 1O₂. Consequently, in the suspension 100 according to the embodiment, when the first pneumatic spring device 1Oi and the second pneumatic spring device 1'O₂ operate in opposite phase, the spring stiffness of the first pneumatic spring device 1Oi and the second pneumatic spring device IO2 rises On the other hand, an operation of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ in the same phase facilitates a gas shifting between the first air chamber Ii of the first pneumatic spring device 1Oi and the second air chamber 2₂ of the second pneumatic spring device 1O₂ and a gas shifting between the second air chamber 2i of the first pneumatic spring device

10₁ and the first air chamber I₂ of the second pneumatic spring device 1O₂. Consequently, in the suspension 100 according to the first embodiment, when the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in the same phase, the spring stiffness of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ lowers, whereby ride comfort is improved. A case in which the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in the same phase is equivalent to a case in which the vehicle 20 travels straight ahead. On the other hand, a case in which the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in opposite phase is equivalent to a case in which the vehicle 20 makes a turn. In the suspension 100 according to the first embodiment, the spring stiffness is high when the first pneumatic spring device 1Oi and the second pneumatic spring device

10₂ operate in opposite phase. Thereby, while attaining ride comfort at a low spring stiffness during straight- ahead traveling of the vehicle 20, roll stiffness is enhanced by a high spring stiffness during a turn of the vehicle 20, therefore, driving stability when the vehicle 20 turns can be enhanced. The suspension 100 can thus realize both ride comfort and driving stability and the like during a turn.

The suspension 100 according to the first embodiment makes respective first air chambers and respective second air chambers included in a pair of different pneumatic spring devices communicate with each other and functions, when the vehicle 20 turns, in the same manner as a mechanical stabilizer against vehicle body rolling. Therefore, without providing a mechanical stabilizer against vehicle body roll, an effect that is obtained when a stabilizer is provided can be obtained. Consequently, no mechanical stabilizer is required, which contributes to a weight reduction. Moreover, because the air balanced between the air chambers raises roll stiffness, no electrical control is required. This enhances cost performance. When a mechanical stabilizer that is high in torsional rigidity is used to enhance roll stiffness, ride comfort is deteriorated when one of the wheels passes over a bump or an influence on driveability occurs. However, because the suspension 100 according to the embodiment has a low spring stiffness when the first pneumatic spring device 101 and the second pneumatic spring device 102 operate in the same phase, the deterioration in ride comfort can be suppressed and the influence on handling can be reduced.

In the suspension 100 shown in Fig. 2A, by supplying a gas from gas sources 6A and 6B to the pneumatic spring devices 1Oi and IO₂, the height of the vehicle 20 can be adjusted. A switching valve 3Oi is arranged between the gas source 6A and the first system Sl, and between the gas source 6B and the second system S2, a switching valve 3O₂ is arranged. The switching valves 30χ and 3O₂ have check valves 32i and 32₂ and exhaust portions 33_X and 33₂.

If a gas is individually supplied to the first system Sl or the second system S2, it is also possible to differentiate the vehicle height between the left and right or between the front and rear. By thus supplying the first system Sl or the second system S2 with a gas and exhausting the same, the vehicle height can be adjusted at each pneumatic spring device. Accordingly, when, for example, a load acts on the pneumatic spring device, so-called auto- leveling control is also_j possible , which carries out control to maintain a preset vehicle height by use of vehicle height sensors 4O_x and 4O₂.

Due to a gas passing through the first communicating passageway 5χ and the second communicating passageway 5₂, a damping effect (effect to damp gas vibration in the respective air chambers) with a relatively high frequency can be obtained. Furthermore, as shown in Fig. 2A, by providing orifice circuits 7A and 7B in the first communicating passageway 5i and the second communicating passageway 5₂ as vibration damping units and thereby generating a j et and utilizing a dynamic pressure, a damping effect with a relatively low frequency may be generated.

In this example, the orifice circuits 7A and 7B include orifices 7Ao and 7Bo and check valves 7Ar and 7Br. Consequently, because a gas from the first air chambers Ii and I₂ or the second air chambers 2i and 2₂ receives resistance when passing through the orifice circuits 7A and 7B, a damping effect with a relatively low frequency can be obtained. As the vibration damping units, throttle valves or the like can also be used.

When the first pneumatic spring device 1O_x and the second pneumatic spring device 1O₂ expand and contract, the gases in the respective air chambers of the first pneumatic spring device 1Oi ^and "the second pneumatic spring device 1O₂ pass through the inside of the first communicating passageway 5i and the second communicating passageway 5₂. In that process, heat generated in the gas due to damping is released into the atmosphere. Generally, the life of an pneumatic spring is considerably shortened by a rise in temperature of the rubber into which a gas is filled. According to the suspension 100, heat generated due to damping can be released into the atmosphere when the gas in the respective air chambers passes through the inside of the first communicating passageway 5i and the second communicating passageway 5₂. Conseguently, a decline in durability of the rubber of the air chambers included in the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ can be suppressed to prolong the life of the suspension.

Consequently, it is unnecessary to separately provide a device that displays a damping effect in the suspension 100, which is advantageous for simplification in a structure, a weight reduction, and a cost reduction. Here, in addition to the vibration damping units, controls to supply and discharge the gas to and from the first system Sl or the second system S2 may be simultaneously used. This allows obtaining a higher damping effect. Fig. 2C is a schematic for illustrating an example in which the communicating passageways are further provided for communicating air chambers to circulate a gas between the air chambers. In a suspension 100', the first air chamber I₁ of the first pneumatic spring device 1Oi and the second air chamber 2₂ of the second pneumatic spring device IO₂ are communicated with each other via the first communicating passageway 5χ. In addition, the second air chamber 2χ of the first pneumatic spring device 1O₁ and the first air chamber I₂ of the second pneumatic spring device IO₂ are communicated with each other via the second communicating passageway 5₂. In the first communicating passageway 5χ, an orifice 15χ and a check valve 14χ are provided, and in the second communicating passageway 5₂ , an orifice 15₂ and a check valve 14₂ are provided. Then, the orifices 15χ and 15₂ and check valves 14χ and 14₂ provide a damping effect.

In the suspension 100', the first air chamber I₁ of the first pneumatic spring device 10χ and the second air ■ chamber 2₂ of the second pneumatic spring device 1O₂ are communicated with each other via a first circulating passageway 13χ. The second air chamber 2χ of the first pneumatic spring device 1O₁ ^'and the first air chamber 12 of the second pneumatic spring device 1O₂ are communicated with each other via a second circulating passageway 13₂. In the first circulating passageway 13χ, an orifice 17χ and a check valve 16χ are provided, and in the second circulating passageway 13₂, an orifice 17₂ and a check valve 16₂ are provided. Then, the orifices 17χ and 17₂ and check valves 16χ and 16₂ provide a damping effect.

Because the gas in the first air chamber I₁ of the first pneumatic spring device 10χ and the gas in the second air chamber 2₂ of the second pneumatic spring device 1O₂ are communicated with each other by the first communicating passageway 5χ and the first circulating passageway 13χ, the gases are integrated as a closed gas (first circulation system SSl) . In addition, because the gas in the second air chamber 2i of the first pneumatic spring device 1O₁ and the gas in the first air chamber I₂ of the second pneumatic spring device 1O₂ are communicated with each other by the second communicating passageway 5₂ and the second circulating passageway 13₂, the gases are integrated as a closed gas (second circulation system SS2) .

When the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ expand and contract, the gases in the respective air chambers of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ circulate inside of the first circulation system SSl and the second circulation system SS2. In that process, heat generated in the gas due to damping is released into the atmosphere when the gas passes through the first and the second communicating passageways 5i and 5₂ and the first and the second circulating passageways 13i and 13₂.

According to the suspension 100', by providing the first and the second circulating passageways 13i and 13₂ to circulate the gas in the first circulation system SSl and the second circulation system SS2 , heat in the gas can be more efficiently released. Consequently, a decline in durability of the rubber of the air chambers included in the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ can be suppressed to prolong the life of the suspension. The cooling structure herein explained can also be applied to the following examples as appropriate .

Fig. 3A is a schematic for illustrating a piping example where the first and the second air chambers included in the pneumatic spring devices according to a first modification of the present embodiment are all connected. Fig. 3B is a schematic for illustrating a piping example that shows a condition in which, all air chambers included in the respective pneumatic spring devices are communicated in a pair of pneumatic spring devices. A suspension 100a is roughly the same in construction as the suspension 100 but is different therefrom in having a switching valve 8 being a passageway opening and closing unit between the first communicating passageway 5i and the second communicating passageway 5₂.

The switching valve 8 communicates between the first communicating passageway 5χ and the second communicating passageway 5₂ or shut off the same by switching a shutoff portion 8c and a communication portion 8o by use of an actuator 8s. In the suspension 100a, when the switching valve 8 is closed by a controller 22, communication between the first communicating passageway 5χ and the second communicating passageway 5₂ is shut off. In this case, the first air chamber Ii of the first pneumatic spring device 1Oi and the second air chamber 2₂ of the second pneumatic spring device 1O₂ are integrated as a closed gas, and the second air chamber 2χ of the first pneumatic spring device 1Oi and the first air chamber I₂ of the second pneumatic spring device 1O₂ are integrated as a closed gas. Thereby, actions and effects the same as those in the suspension 100 according to the embodiment can be obtained.

In the suspension 100a, when the switching valve 8 is opened, the first communicating passageway 5i and the second communicating passageway 5₂ are communicated with each other. Thereby, the first air chamber Ii and the second air chamber 2i of the first pneumatic spring device 1Oi and the first air chamber I₂ and the second air chamber 2₂ of the second pneumatic spring device 1O₂ are all communicated with each other. Namely, as shown in Fig. 3B, it results in a condition where the first air chamber Ii and the second air chamber 2i of the first pneumatic spring device 10χ and the first air chamber I₂ and the second air chamber 2₂ of the second pneumatic spring device 1O₂ are connected via a first-chamber communicating passageway 5el and a second-chamber communicating passageway 5e₂. Namely, all air chambers included in the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ are integrated as a closed gas. The spring stiffness in this condition is equivalent to that when air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are communicated with each other, that is, when the first air chambers I₁ and I₂ are communicated with each other and the second air chambers 2χ and 2₂ are communicated with each other, and obtained actions and effects are also equivalent. When the switching valve 8 is opened, the spring stiffness of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ when these operate in the same phase becomes lower than that when the switching valve 8 is closed. Accordingly, when the spring stiffness of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ operate in the same phase, that is, when the vehicle 20 is straight-ahead traveling, the spring stiffness can be switched in two stages. This allows placing priority on ride comfort or on driving performance according to the situation. When the vehicle 20 is turning, because roll stiffness can be enhanced by closing the switching valve 8 in comparison with when straight-ahead traveling, driving stability of the vehicle 20 can be enhanced. In the suspension 100a, it is possible to anticipate a running situation of the vehicle 20 based on information obtained from a CCD sensor, a car navigation system, a rotation angle of a steering wheel, or the like and switch piping of the pneumatic spring devices according thereto . For example, by normally opening the switching valve 8 to secure ride comfort and then closing the switching valve 8 when it is discovered that there is a curve ahead in the traveling direction based on information from a car navigation system, a rotation angle of a steering wheel, or the like before the vehicle enters the curve, roll stiffness can be enhanced. In addition, the steering wheel angle can be measured by use of a steering angle sensor, and is used to control valve lift of the switching valve 8.

Fig. 4 is a schematic for illustrating an example in which air chambers between the pneumatic spring devices according to a second modification of the present embodiment attached in front and rear of the vehicle are connected. The direction of an arrow L in Fig. 4 represents a traveling direction of the vehicle 20. According to the second modification, between a pair of pneumatic spring devices at the same side and in the front and rear of the vehicle, air chambers included in the respective pneumatic spring devices are communicated with each other. In detail, as shown in Fig. 4, between the first pneumatic spring device 1Oi and a third pneumatic spring device IO₃ being a pair of pneumatic spring devices attached at the same side and in the front and rear of the vehicle and between the second pneumatic spring device IO2 and a fourth pneumatic spring device IO₄ being the same pair of pneumatic spring devices, air chambers of the respective pneumatic spring devices are communicated.

In this example, the first air chamber lχ of the first pneumatic spring device 1Oi and a second air chamber 2₃ of the third pneumatic spring device IO₃ are connected to each other via the first communicating passageway 5χ, and the second air chamber 2χ of the first pneumatic spring device 1Oi and a first air chamber I₃ of the third pneumatic spring device 1O₃ are connected to each other via the second communicating passageway 5₂. In addition, the first air chamber I₂ of the second pneumatic spring device 1O₂ and a second air chamber 2₄ of the fourth pneumatic spring device ICU are connected to each other via the first communicating passageway 5χ, and the second air chamber 2₂ of the second pneumatic spring device 1O₂ and a first air chamber I₄ of the fourth pneumatic spring device IO₄ are connected to each other via the second communicating passageway 52. Because this makes it possible to increase pitch stiffness in a suspension 100b, pitching of the vehicle 20 can be suppressed while deterioration in ride comfort of the vehicle 20 is suppressed. As shown in Fig. 4, in the suspension 100b, a first switching valve 8₁ may be provided between the first communicating passageway 5χ and the second communicating passageway 5₂ on the side of the first pneumatic spring device 1Oi , and between the first communicating passageway 5i and the second communicating passageway 5₂ on the side of the second pneumatic spring device 1O₂. This allows opening and closing the first switching valves 8₁ and a second switching valve 8₂ according to the running condition of the vehicle 20 to increase pitch stiffness and improve ride comfort. For example, the first and the second switching valves 8₁ and 8₂ are opened during normal running to enhance ride comfort, and during braking, the first and the second switching valves 8₁ and 8₂ are closed to suppress the vehicle 20 from nose diving in the front. Fig. 5 is a schematic for illustrating an example in which, air chambers are connected between each pair of the pneumatic spring devices according to a third modification of the present embodiment located at diagonal positions. The direction of an arrow L in Fig. 5 represents a traveling direction of the vehicle 20. In detail, as shown in Fig. 5, of the pneumatic spring devices attached to four points of the vehicle 20, between the first pneumatic spring device 1Oi and the fourth pneumatic spring device 1O₄ being a pair of pneumatic spring devices located at diagonal positions and between the second pneumatic spring device 1O₂ and the third pneumatic spring device IO₃ being a pair of pneumatic spring devices, air chambers of the respective pneumatic spring devices are communicated with each other.

In this example, as shown in Fig. 5, the first air chamber I₁ of the first pneumatic spring device 1Oi and the second air chamber 2₄ of the fourth pneumatic spring device 1O₄ are connected to each other via the first communicating passageway 5χ, and the second air chamber 2χ of the first pneumatic spring device 1Oi and the first air chamber I₄ of the fourth pneumatic spring device 1O₄ are connected to each other via the second communicating passageway 5₂. In addition, the first air chamber I₂ of the second pneumatic spring device 1O₂ and the second air chamber 2₃ of the third pneumatic spring device 1O₃ are connected to each other ' via ^' a first communicating passageway 5₃, and the second air chamber 2₂ of the second pneumatic spring device 1O₂ and a first air chamber I₃ of the third pneumatic spring device 1O₃ are connected to each other via a second communicating passageway 5₄. Therefore, it is possible to increase diagonal stiffness in a suspension 100c. Namely, because combination stiffness of pitching and rolling can be increased, a combination of pitching and rolling of the vehicle 20 can be suppressed while a deterioration in ride comfort of the vehicle 20 is suppressed.

In the suspension 100c, the first switching valve 81 may be provided between the first communicating passageway 5χ and the second communicating passageway 5₂ on the side of the first pneumatic spring device 1Oi , and between the first communicating passageway 5₃ and the second communicating passageway 5₄ on the side of the second pneumatic spring device 1O₂. This allows opening and closing the first and the second switching valves 8χ and 8₂ according to the running condition of the vehicle 20 to increase pitching and roll stiffness and improve ride comfort. For example, the first and the second switching valves 8i and 8₂ are opened during normal running to enhance ride comfort, and during turning or braking, the first and the second switching valves 8i and 8₂ are closed to suppress the vehicle 20 from rolling or nose diving in the front.

Fig. 6A is a schematic for illustrating a piping example where a first air chamber and a second air chamber included in an identical pneumatic spring device according to a fourth modification of the present invention are connected. Fig. 6B is a schematic for illustrating a condition in which the pneumatic spring devices according to the fourth modification are attached to front, rear, left, and right of the vehicle. The direction of an arrow L in Fig. 6B represents a traveling direction of the vehicle 20. For a suspension 10Od, in pneumatic spring devices attached to the vehicle 20, the first air chamber and the second air chamber of each identical pneumatic spring device are communicated with each other via a communicating passageway, and a switching valve being a passageway opening and closing unit is provided in the communicating passageway. Operation of the switching valve is controlled by a suspension controller.

For example, the first air chamber Ii and the second air chamber 2i of the first pneumatic spring device 1O_x are connected with each other via communicating passageways 5di to 5d₄, and in the middle of the communicating passageway 5di , a switching valve 9χ is provided. Similarly, the respective first air chambers Ii and second air chambers 2_± of the second to the fourth pneumatic spring devices 1O₂ to 1O₄ are connected with each other via communicating passageways 5d₂ to 5d₄, respectively, and in the middle of the respective communicating passageways, switching valves 9₂ to 9₄ are provided. Operation of the respective switching valves 9χ to 9₄ are controlled by a suspension controller 23.

When the respective switching valves 9i to 9₄ are closed to communicate the first air chambers and the second air chambers of the first to the fourth pneumatic spring devices 1O₁ to 1O₄ with each other, the spring stiffness is lowered to about one-half in comparison with that when communication between the first air chamber and the second air chamber is shut off. Accordingly, when the vehicle 20 is straight-ahead traveling, the respective switching valves 9i to 9₄ are opened by the suspension controller 23 to improve ride comfort.

On the other hand, when the vehicle 20 is turning, the switching valves corresponding to pneumatic spring devices (the second and the fourth pneumatic spring devices 1O₂ and 1O₄ when turning to the left, and the first and the third pneumatic spring devices 10χ and 1O₃ when turning to the right) positioned at the outside of the curve are closed. Thereby, because the pneumatic spring devices at the outside of the curve are raised in the spring stiffness, roll stiffness of the suspension lOOd is enhanced. Thereby, handling and driving performance of the vehicle 20 are enhanced. In addition, during braking, the switching valves 9i and 9₂ corresponding to the pneumatic spring devices (first and second pneumatic spring devices 1Oi and 1O₂) at the front side in the traveling direction of the vehicle 20 are closed. Thereby, because pitch stiffnee of the vehicle 20 is enhanced, this can suppress the vehicle 20 from nose diving in the front.

Fig. 7 is a schematic for illustrating an attaching structure when the pneumatic spring device according to the first embodiment is applied to a double wishbone-type suspension. In this type of suspension, an upper arm 14 of a double wishbone penetrates through the though hole 12 provided in the case 11 of the pneumatic spring device 10. The upper arm 14 is fixed to the load carrying member 3 of the pneumatic spring device 10, and a force input from the upper arm 14 is transmitted to the first air chamber 1 and the second air chamber 2 by the load carrying member 3. As such, in the double wishbone-type suspension, the upper arm 14 serves as a loading member. Because the pneumatic spring device 10 can be shortened in overall length, the suspension as a whole can be designed compact.

Fig. 8 is a schematic for illustrating an attaching structure when the pneumatic spring device according to the first embodiment is applied to a swing axle-type suspension. In this type of suspension, a half shaft 13 of a swing axle penetrates through the though hole 12 provided in the case 11 of the pneumatic spring device 10. The half shaft 13 is fixed to the load carrying member 3 of the pneumatic spring device 10 so as to be swingable, and a force input from the half shaft 13 is transmitted to the first air chamber 1 and the second air chamber 2 by the load carrying member 3. As such, in the swing axle-type suspension, the half shaft 13 serves as a loading member.

In the swing axle-type suspension, a so-called jacking phenomenon, in which the camber angle of the wheels at the outside of the curve is increased to suddenly lift the vehicle body, occurs in sharp turn. In the pneumatic spring device 10 according to the embodiment, because the half shaft 13 penetrates through the through-hole 12 provided in the case of the pneumatic spring device 10, the camber angle of wheels at the outside of the corner are not increased beyond a certain size. When the camber angle is increased because the half shaft 13 makes contact against the lower end (end on the side opposite from the side of attachment to the vehicle 20) of the through-hole and does not shift any further, an increase in the camber angle stops at this position. Therefore, when the pneumatic spring device 10 according to the embodiment is applied to the swing axle-type suspension, jacking can be prevented to attain driving stability.

Fig. 9 is a schematic for illustrating an attaching structure when the pneumatic spring device according to the first embodiment is applied to a strut-type suspension. In this type of suspension, the loading member 4 rigidly coupled with a hub 15 penetrates through the through-hole 12 provided in the case 11 of the pneumatic spring device 10. The loading member 4 is fixed to the load carrying member 3 of the pneumatic spring device 10, and a force input from the loading member 4 is transmitted from the first air chamber 1 and the second air chamber 2 by the load carrying member 3. In this example, the pneumatic spring device 10 is rigidly coupled with the vehicle 20. Because the pneumatic spring device 10 can be shortened in overall length, the suspension as a whole can be made compact .

The suspensions according to the first embodiment and modifications thereof support a load by the first air chambers and the second air chambers, and includes the communicating passageways that communicate the first air chambers and the second air chambers with each other. Therefore, by, for example, opening and closing the communicating passageways, the spring stiffness of the pneumatic spring devices can be easily changed according to the running condition of the vehicle.

In addition, by communicating the respective first air chambers and the respective second air chambers owned by different pneumatic spring devices with each other, an effect is provided, when the pneumatic spring devices attempt to operate in opposite phase, so as to suppress each other's operation. By arranging such a pair of pneumatic spring devices in the left and right or front and rear of the vehicle or diagonally, roll stiffness and pitch stiffness can be automatically enhanced during straight- ahead traveling. Consequently, the spring stiffness of the pneumatic spring devices can be easily changed according to the running condition of the vehicle. Thus, handling and driving performance suitable to the running condition of the vehicle such as straight-ahead traveling or turn traveling can be obtained.

Actions and effects the same as those of the embodiment and modifications thereof can be achieved as long as a construction the same as that of the embodiment and modifications is provided. Moreover, the embodiment and modifications can be used in appropriate combination with the following embodiment.

Figs. 1OA to 1OC are schematics for illustrating an example in which air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are connected to each other between different pneumatic spring devices, according to a second embodiment of the present invention. Fig. 1OA is a schematic of an example where the first air chambers Ii and I₂ of the first pneumatic spring device 1Oi and the second pneumatic spring device IO2 are connected to each other via a communicating passageway 5e. Fig. 1OB is a schematic of an example where the second air chambers 2_X and 2₂ of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ are connected to each other via the communicating passageway 5e. Fig. 1OC is a schematic of an example where the first air chambers Ii and I₂ and the second air chambers 2i and 2₂ of the first pneumatic spring device 1Oi and the second pneumatic spring device 1O₂ are connected to each other via the first-chamber communicating passageway 5ei and the second-chamber communicating passageway 5e₂, respectively.

For example, in the piping connection example shown in Fig. 1OC , if the first load carrying member 3i of the first pneumatic spring device 1Oi shifts to the side of the first air chamber Ii , a gas shifts from the first air chamber Ii of the first pneumatic spring device 1Oi to the first air chamber I₂ of the second pneumatic spring device 1O₂. In addition, a gas shifts from the second air chamber 2₂ of the second pneumatic spring device 1O₂ to the second air chamber 2χ of the first pneumatic spring device 1Oi . Thereby, due to the gas shifting, the second load carrying member 3₂ of the second pneumatic spring device device 1O₂ shifts in a direction opposite from the shifting direction of the first load carrying member 3i of the first pneumatic spring device 1Oi , that is, in opposite phase. In other words, the shifting direction of the first load carrying member 3i of the first pneumatic spring device 1Oi is opposite from the shifting direction of the second load carrying member 3₂ of the second pneumatic spring device 1O₂. At this time, there is little change in pressure in the respective air chambers or in load. Although there is a compression and expansion of the gas in the air chambers not communicated in the piping connection example shown in Fig. 1OA and Fig. 1OB, operation is the same as that in the piping connection example shown in Fig. 1OC.

In such a manner, when, between different pneumatic spring devices, air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are communicated with each other, the different pneumatic spring devices can be expanded and contracted in different directions respectively by a very small force. When pneumatic spring devices to which the piping connection has been applied are used for a suspension of the vehicle 20, the spring stiffness can be further lowered in comparison to when the first air chamber and the second air chamber of each identical pneumatic spring device are communicated with each other. Accordingly, when the air chambers at the same side with respect to an expanding and contracting direction of pneumatic spring devices are communicated with each other, this is suitable for obtaining better ride comfort when stable running of the vehicle 20 has been secured. The spring stiffness is lower when only the second air chambers are communicated with each other in a pair of pneumatic spring devices , only the first air chambers are communicated with each other in a pair of pneumatic spring devices, and the first air chambers are communicated with each other and the second sir chambers are communicated with each other in a pair of pneumatic spring devices, in this order. Accordingly, the spring stiffness can be adjusted by changing the air chambers to be communicated by use of a piping switching device or the like. Here, between a pair of pneumatic spring devices arranged in the left and right of the vehicle 20, between a pair of pneumatic spring devices arranged in the front and rear of the vehicle 20 and at the same side, or between a pair of pneumatic spring devices arranged at diagonal positions of the vehicle 20, it is preferable to communicate air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices with each other.

Fig. 11 is a schematic for illustrating a piping example in which air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are connected to each other between different pneumatic spring devices . Between different pneumatic spring devices, when air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices are communicated with each other, as shown in Fig. 11, between the different pneumatic spring devices, which are attached to the left and right of the vehicle, the first air chamber and the second air chamber of the different pneumatic spring devices are communicated with each other via a second switching valve 25₂ to enhance roll stiffness. Here, because there are two combinations between the first air chamber and the second air chamber in the different pneumatic spring devices, both combinations are communicated with each other. Moreover, between the different pneumatic spring devices, a first switching valve 25i is provided in piping to connect the air chambers at the same side with respect to an expanding and contracting direction of the pneumatic spring devices .

By such a construction, when the vehicle 20 turns, the first switching valve 25i is closed and the second switching valve 25₂ is opened by a controller 24 to communicate the first air chamber Ii of the first pneumatic spring device 10χ and the second air chamber 2₂ of the second pneumatic spring device 1O₂ with each other and communicate the second air chamber 2i of the first pneumatic spring device 1Oi and the first air chamber I₂ of the second pneumatic spring device 1O₂ with each other. Thereby, because roll stiffness can be enhanced, driving performance of the vehicle 20 is enhanced and good handling can be obtained.

During straight-ahead traveling, by closing the second switching valve 25₂ and opening the first switching valve 25i by the controller 24, the first air chamber Ii of the first pneumatic spring device 1Oi and the first air chamber I₂ of the second pneumatic spring device 1O₂ are communicated with each other and the second air chamber 2i of the first pneumatic spring device 1Oi and the second air chamber 2₂ of the second pneumatic spring device 1O₂ are¹ communicated with each other. Thereby, ride comfort can be secured during straight-ahead traveling. In this case, because the spring stiffness is lower than when the second switching valve 25₂ is opened and the first switching valve

25₁ is closed, ride comfort can be enhanced from that in such a case. During straight-ahead traveling, the second switching valve 25₂ may be opened and the first switching valve 25i may be closed. In this case, because the spring stiffness is higher than when the second switching valve

25₂ is closed and the first switching valve 25i is opened, when the vehicle 20 using a suspension according to this example travels straight ahead, the spring stiffness can be switched in two stages .

INDUSTRIAL APPLICABILITY As in the above, the suspension according to the present invention is useful for a vehicle suspension and is suitable particularly to change the spring stiffness according to the running condition of a vehicle.

Claims

1 . A suspens ion comprising : a plurality of pneumatic spring devices that is attached to different positions of a vehicle to support a vehicle weight, each of the pneumatic spring devices including a first air chamber that supports a load by a gas confined inside; and a second air chamber that supports the load with the first air chamber by a gas confined inside; a first communicating passageway that communicates, in a pair of the pneumatic spring devices, the first air chamber included in one pneumatic spring device with the second air chamber included in other pneumatic spring device; and a second communicating passageway that communicate the second air chamber included in the one pneumatic spring device with the first air chamber included in the other pneumatic spring device, wherein an effective load carrying area of the second air chamber is smaller than that of the first air chamber, and a volume change of the second air chamber is opposite from a volume change of the first air chamber, when a load is placed.

2. The suspension according to claim 1, wherein the pair of the pneumatic spring devices is attached to left and right of the vehicle.

3. The suspension according to claim 1, wherein the pair of pneumatic spring devices is attached to front and rear of the vehicle at a same side.

4. The suspension according to claim 1, wherein the pair of pneumatic spring devices is attached to diagonal positions of the vehicle.

5. The suspension according to any one of claims 1 to 4 , wherein at least one of a passageway switching unit and a throttle valve unit is provided between the first communicating passageway and the second communicating passageway.

6. The suspension according to claim 1, further comprising: a circulating passageway to connect the first air chamber and the second air chamber.

7. The suspension according to claim 1, wherein the communicating passageway includes a vibration damping unit that attenuates a vibration of the gas .

8. The suspension according to any one of claims 1 to 7, wherein a stopper member that generates a non-impulsive repulsive force when compressed toward an operating direction of the pneumatic spring device is provided in the first air chamber.

9. A suspension comprising: a plurality of pneumatic spring devices that is attached to different positions of a vehicle to ease an impact from a wheel, each of the pneumatic spring devices including a first air chamber in which a gas is confined; a second air chamber in which a gas is confined, being arranged opposite the first air chamber; and a load acarrying member that is supported by the first air chamber and the second air chamber; and a communicating passageway that communicates the first air chamber with the second air chamber, wherein an effective load carrying area of a part of the load carrying member, which makes contact with the first air chamber, is greater than an effective load carrying area of a part of the load carrying member, which makes contact with the second air chamber.

10. The suspension according to claim 9, wherein the communicating passageway includes a passageway switching unit that opens and closes the communicating passageway .

11. The suspension according to claim 9, wherein the communicating passageway includes a vibration damping unit that attenuates a vibration of the gas.

12. The suspension according to claim 9, wherein the second air chamber is arranged lower side than the first air chamber in a vertical direction, the load carrying member is sandwiched between the first air chamber and the second air chamber, and the load carrying member includes a loading member that transmits the impact from the wheel to the load carrying member.

13. The suspension according to claim 12, wherein the first air chamber and the second air chamber are stored in a chassis, and the loading member is penetrated through a through- hole provided in the chassis .

14. The suspension according to any one of claims 9 to 13, wherein a stopper member that generates a non-impulsive repulsive force when compressed toward an operating direction of the pneumatic spring device is provided in the first air chamber, at least on a side of attachment of the pneumatic spring device to the vehicle or a side of the load carrying member.