Suspension system for vehicles

In a switchable suspension system for automobiles and other vehicles, an auxiliary air-spring chamber is provided above a main air-spring chamber in such a manner as to enclose a piston rod so that the spring force of the suspension can be adjusted appropriately. An air passage to connect the two air-spring chambers is provided in the piston rod. The piston rod and a control rod extending inside the piston rod make up a switch valve that controls the opening and closing of the air passage. The air passage of the suspension system is enclosed with a cover to cut off the outward leakage of the noise resulting from the inflow and outflow of air through the air passage that leads from an air compressor to the two air-spring chambers of the suspension system.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an improvement in the suspension system for 
vehicles equipped with an air-spring-assisted car-height adjusting 
mechanism. 
2. Description of the Prior Art 
Some suspension systems for vehicles are equipped with an 
air-spring-assisted car-height adjusting mechanism. 
With this type of conventional suspension systems, however, it has been 
impossible to change the spring constant freely in accordance with the 
varying running conditions while maintaining a given car height. So, if 
the spring constant is preliminarily set at a lower level, the car body 
rolls and/or pitches heavily, with a resulting impairment of steering 
stability, when it is exposed to external force. If, on the other hand, 
the spring constant is set at a higher level to secure steering stability, 
riding comfort is reduced. 
This type of suspension systems also has a modified version which comprises 
an auxiliary air-spring chamber of a given capacity connected to a main 
air-spring chamber and a switch valve interposed between the two 
air-spring chambers. When the switch valve is closed, a relatively large 
spring force is obtained by use of the air contained in the main 
air-spring chamber alone. When the switch valve is opened, a relatively 
small spring force is obtained by use of the air contained in the main and 
auxiliary air-spring chambers. 
This modified version also has not been without shortcomings. Because the 
auxiliary air-spring chamber is positioned away from the suspension strut, 
it is necessary to secure a space to place the auxiliary air-spring 
chamber itself, a passage interconnecting the two air-spring chambers, and 
the switch valve. It is also necessary to provide some means to protect 
the interconnecting passage and switch valve. 
SUMMARY OF THE INVENTION 
This invention has been made in order to obviate the above-described 
shortcomings with the conventional suspension systems for vehicles. 
An object of this invention is to provide a suspension system for vehicles 
which comprises a main air-spring chamber, an auxiliary air-spring 
chamber, a passage interconnecting the two air-spring chambers, and a 
switch valve which is capable of varying the effective capacity of the 
air-spring chambers, with the auxiliary air-spring chamber and switch 
valve incorporated in a highly compact manner. 
Another object of this invention is to provide a suspension system for 
vehicles equipped with the two air-spring chambers as described above in 
which a damping-capacity switching mechanism attached to a shock absorber 
is actuated simultaneously with the connection and disconnection of the 
two air-spring chambers. 
Still another object of this invention is to provide a suspension system 
for vehicles equipped with the two air-spring chambers as described above 
in which the auxiliary air-spring chambers is adapted to function as a 
spring bearing to support the upper end of a coil spring disposed in 
parallel with the air-spring chamber for system parts and size reduction. 
Yet another object of this invention is to provide a similar suspension 
system for vehicles which is adapted to reduce the noise that is produced 
as air flows in and out of the two air-spring chambers when car-height is 
adjusted. 
In order to achieve the objects just described, the improvement according 
to this invention in the suspension system for vehicles having a shock 
absorber comprising a cylinder supporting an axle, a piston fitted in the 
cylinder, dividing the space within the cylinder into two chambers and 
having orifice passages intercommunicating the two chambers, and a piston 
rod extending upward from the piston with the upper end thereof supported 
by the car body is characterized as follows: A main air-spring chamber is 
provided coaxially around the piston rod and cylinder to support the 
weight of the car body. An auxiliary air-spring chamber is disposed 
coaxially around the piston rod and above the main air-spring chamber. A 
control rod which extends in the longitudinal direction of the piston rod 
and permits displacement with respect thereto is provided in the piston 
rod. The peripheral wall of the piston rod surrounding the control rod is 
provided with an opening communicating with the main and auxiliary 
air-spring chambers. The control rod has an air passage that connects the 
main and auxiliary air-spring chambers through the opening in the piston 
rod and permits air to be supplied into and discharged from the two 
air-spring chambers. The piston and control rods are designed to function 
as a switch valve that selectively connects and disconnects the main and 
auxiliary air-spring chambers through the displacement of the control rod 
with respect to the piston rod. Furthermore, a silencing cover to reduce 
the outward leakage of the noise resulting from the flow of air through 
the air passage in the control rod is provided in such a manner as to 
enclose the upper end of the piston rod. 
Accordingly, the suspension system for vehicles according to this invention 
provides the following desirable effects or advantages: 
(1) Riding comfort and safety are increased by keeping the car's wheels in 
firm contact with the road and enhancing steering stability depending upon 
the acceleration and other factors working on the car body while keeping 
the car height at a given level through the variation of the damping 
capacity of the shock absorber and the spring constant of the air-spring 
chambers. 
(2) An air-spring chamber consists of a main and auxiliary air-spring 
chamber, with a switch valve provided therebetween. The spring constant 
can be changed easily since the capacity of the air-spring chamber is 
varied by connecting or disconnecting the two air-spring chambers through 
the actuation of the switch valve. 
(3) The auxiliary air-spring chamber and switch valve can be compactly 
built in a suspension system equipped with the main air-spring chamber. 
(4) The spring constant of the air spring and the damping capacity of the 
shock absorber can be changed simultaneously. 
(5) With the bottom surface of the auxiliary air-spring chamber serving 
also as a spring bearing to support the upper end of the coil spring, both 
the number of parts and the size of the entire system can be reduced. 
(6) The outward leakage of the noise caused by the air supplied to and 
discharged from the two air-spring chambers for car-height adjustment can 
be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The structure and function of a suspension system for vehicles according to 
this invention will be described in detail hereunder by reference to the 
accompanying drawing. 
The suspension system illustrated is of the strut type, in which reference 
numeral 1 designates a damping-capacity switchable shock absorber which 
comprises a cylinder 2 fastened to the wheel side, a piston 5 fitted in 
the cylinder 2 and dividing the internal space thereof into two hydraulic 
chambers 3a and 3b, orifice passages 6a, 6b and 6c provided in the piston 
5 to connect the two hydraulic chambers 3a and 3b, a piston rod 4 
extending upward from the piston 5, a control rod 7 axially extending 
inside the piston rod 4 and capable of rotating with respect thereto, a 
control valve 8 attached to the lower end of the control rod 7 to change 
the effective cross-sectional area of the orifice passages, and an 
actuator that activates the control valve 8 through the control rod 7. 
This damping capacity switchable shock absorber 1 effectively absorbs a 
shock with its damping function that is exercised depending upon the 
position of the control valve 8 as a cylinder 2 outside the car body moves 
up and down with respect to the piston rod 4 as the wheel travels up and 
down. On top of the shock absorber 1, there is provided a main air-spring 
chamber 9 that coaxially encloses the piston rod 4 and cylinder 2, with an 
auxiliary air-spring chamber 10 resting directly thereon in such a manner 
as to enclose said piston rod 4 that is disposed coaxially therewith. The 
two air-spring chambers 9 and 10 communicate with each other through an 
air passage 11 formed in the control rod 7, communicating passages 12a and 
12b in that portion of the piston rod 4 which surrounds the control rod 7, 
and communicating passages 13a and 13b in the control rod 7. 
When the position of the control rod 7 is changed by rotating, the piston 
rod 4 and control rod 7, in combination, function as a switch valve 14 
that connects and disconnects the two air-spring chambers 9 and 10. 
Opening and closing the switch valve 14 connects and disconnects the two 
air-spring chambers 9 and 10, thereby varying the air volume contained in 
the air-spring chamber and the spring constant of the suspension. 
The control valve 8 makes the cross-sectional area of the orifice passages 
smaller when the switch valve 14 is closed by the control rod 7 than when 
the switch valve 14 is open. 
Car height is adjusted by varying the air volume in the air-spring chamber 
9 or in the two air-spring chambers 9 and 10. To a coupling port 15 above 
the air passage 11 is connected a pipe 16 leading to an air compressor. A 
solenoid valve is provided midway in the pipe 16. Car height is adjusted 
by allowing air to flow into and out of the air-spring chambers 9 and 10 
through the air passage 11, depending upon the car height or other 
conditions detected, through the actuation of the solenoid valve. 
Reference numeral 19 designates a coil spring that is disposed in such a 
manner as to enclose the main air-spring chamber 9, with the lower end 
thereof supported by a sprng bearing 17 fastened to the cylinder 2 and the 
upper end thereof by the bottom surface 18 of the auxiliary air-spring 
chamber 10 that projects radially beyond the periphery of the main 
air-spring chamber 9. 
Reference numeral 20 denotes a bellows forming a part of the main 
air-spring chamber 9, 21 a bearing, 22 a bracket fastening the suspension 
system through the bearing 21 to a body frame 23, 24 a rubber mount fitted 
in the bracket 22, 25 a cover attached to the body frame 23 in such a 
manner as to enclose the upper end of the suspension system, and 26 a hole 
provided in the cover 25 to pass the pipe 16. 
Thus, the auxiliary air-spring chamber 10 is placed above the main 
air-spring chamber 9 in such a manner as to enclose the piston rod 4. The 
two air-spring chambers 9 and 10 are connected through the communicating 
passages 12a, 12b, 13a, 13b and the air passage 11 provided in the piston 
and control rods 4 and 7. When the control rod 7 is rotated to change the 
position thereof with respect to the piston rod 4, the two rods, in 
combination, serve as a switch valve 14 that selectively connects and 
disconnects the two air-spring chambers 9 and 10. This arrangement is 
conducive to making the entire system into a highly compact unit. 
With the control valve 8 adapted to change the effective cross-sectional 
area of the orifice passages in the piston 5 is attached to the lower end 
of the control rod 7, the spring force and damping capacity of the 
suspension can be switched simultaneously through the rotation of the 
control rod 7 and the resulting actuation of the switch valve 14. 
Since the auxiliary air-spring chamber 10 radially projects beyond the 
periphery of the main air-spring chamber 9, the bottom surface 18 of the 
auxiliary air-spring chamber 10 serves as the spring bearing to support te 
upper end of the coil spring 19. This eliminates the need for providing a 
special spring bearing for supporting the upper end of the coil spring 19, 
thereby permitting to reduce the number of parts and the system size. 
A cover 25 to enclose the coupling port 15 and other parts at the top of 
the suspension system is attached to the body frame 23. The cover 25 is 
effective in materially reducing the outward leakage of the noise 
generated around the air passage 11 and coupling port 15. A greater 
silencing effect can be attained by lining the inside of the cover 25 with 
an acoustic absorber not shown.