Stabilizer fitting apparatus

The reciprocal device is interposed between an end of of a torsion bar and the swing arm of a suspension system for a front wheel of a vehicle so as to reciprocate in both the extensional and intensional directions with the stroke thereof being limited to a length remarkably smaller than the maximum amplitude of the ends of the torsion bar, in response to the movement of the torsion bar. The device has a resisting force that gradually increases while the device is in the advance process from the neutral position to the end of the both strokes but substantially naught when it is in the return process from the end of the stroke to the neutral position.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to an apparatus for fitting a stabilizer to a 
vehicle, particularly to a passenger car. 
A passenger car is generally equipped with a stabilizer applied to a pair 
of front wheels. The stabilizer consists of a U-shaped torsion bar, the 
opposite ends of which are so connected to the right and left wheels that 
the torsional resistance of the bar relieves the car from an inclination 
to one side due to the centrifugal force, while the car turns. Most modern 
vehicles are designed to be equipped with an independent suspension system 
for the front wheels, in which each wheel behaves independently from and 
is unaffected by the other wheel for the purpose of suppressing rolling 
when traveling straight. High speed operation requires a stabilizer 
assembly with a stronger torsion bar, but then operation of the supension 
on one side influences the suspension on the other, leading to 
considerable disadvantages. One of the disadvantages is that in the case 
where a wheel passes over a hole in a road when traveling straight, a 
stronger torsion bar would prevent a wheel from dropping completely into 
the hole, producing as consequence poor road-holding performance. In this 
situation, the vehicle would roll more than if a weaker or no torsion bar 
were fitted. Another disadvantage is that, when the vehicle travels 
straight, a relatively large bump would induce more roll than were no 
stabilizer fitted, because the stabilizer and the suspension spring 
overlap each other to bring an excessively strong action. Furthermore, a 
shock absorber is required to have a strong braking force sufficient to 
equal the sum of the spring constants of the respective torsion bar and 
suspension spring, leading to a further disadvantage that move vibrations 
under spring are transmitted the frame of the vehicle creating an 
uncomfortable ride. When one wheel passes over a raised place, the other 
has the road-holding lowered by the torsional resistance in the 
stabilizer, resulting in a poor straight-running performance. 
The apparatus known by my U.S. Pat. No. 4,066,278 and British Pat. No. 
1,514,378 is one that comprises a friction damper assembly of the type 
having a preselected braking force with a predetermined stroke. The 
apparatus has been arranged to absorb the initial distorsion of the 
stabilizer of torsion bar so as to give the vehicle a good 
straight-running performance and a comfortable ride without diminishing 
the anti-roll rigidity of the vehicle. That is, without diminishing the 
resistibility against inclination to one side due to the centrifugal force 
produced during the turning of the vehicle or the resistibility against 
side wind. However, the friction damper remains unmoved when a wheel 
passes over a relatively small bump, because of having the maximum braking 
force when it commences sliding from the neutral position. Accordingly, 
the friction damper maintains no better comfort than when the vehicle 
travels on a good road. The friction damper produces a so-called 
stick-slip accompanying uncomfortable shock and noise in the starting of 
movement. The friction damper has a resisting force that is 
characteristically shown by a flat line without increasing toward the end 
of stroke and substantially identical in the both advance and return 
processes. This is the reason why the piston sometimes fails to reach the 
neutral position and stops at a position slightly before the position in 
the return process, resulting in the fact that the vehicle is caused to 
roll when the wheel behaves rapidly. 
Stabilizer fitting apparatus, such as the friction damper, must be 
contained within the recess of a tire together with other parts, such as a 
brake hose, a brake drum, a lower arm and the like, in order to protect 
themselves from making a contact with a steering wheel. However, the 
apparatus as described above is disadvantageously too large to be 
contained in a restricted space in a small size passenger car. 
It is an object of the present invention to provide a stabilizer assembly 
free from the disadvantages of the prior art. 
This and other objects and advantages of the invention may be readily 
ascertained by referring to the following description and appended 
drawings. 
In accordance with the invention, the stabilizer assembly is capable of 
nullification of the stabilizer-action while in straight-line traveling 
and equipped with means for resolving the instability produced by the 
nullification of the stabilizer-action while turning. The means has a 
resisting force that gradually increases when it is in the advance process 
from the neutral position to the end of the stroke and is substantially 
naught when it is in the return process from the end of the stroke to the 
neutral position.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
Referring to FIG. 1, the vehicle is equipped with a so-called wish-bone 
type independent supension system for a pair of front wheels 1, 2 
including at each side, upper and lower arms 3, 4 each swingably hinged to 
a frame 30 of the vehicle. There are a suspension coil spring 5 and a 
shock absorber 6 interposed between the lower arm 3 and the frame 30. As 
illustrated in FIGS. 1 and 2, a stabilizer is composed of a U-shaped 
torsion bar, which has the central portion twistably mounted on frame 30 
through the intermediary of a couple of rubber bushings 8. Torsion bar 7 
has one end 9 thereof secured to lower arm 3 on one side by a reciprocal 
device 10 and the other end 11 is fixed to the opposite lower arm 3 by a 
bolt assembly 12 of such a length as to keep the device in the neutral 
position when the vehicle is horizontal or level, as seen in FIG. 1. The 
device 10 is arranged to reciprocate both in the extensional and 
intensional directions with an identical length of stroke. Device 10 at 
one end of torsion bar 7 can be replaced by a pair of reciprocal devices 
as shown in FIG, 6, which are disposed at the both ends of the torsion bar 
and have a length of stroke equal to the half of that of the device 10. 
Referring to FIGS. 3 and 4, reciprocal device 10 includes a cylinder 13 and 
a piston 14. Cylinder 13 has the inner diameter thereof being maximum at 
the middle of the length and decreasing toward the opposite ends. The 
cylinder has a tubular rod 33 connected to the end 9 of torsion bar 7 by a 
cushion member 31. Piston 14 has the outer diameter thereof being minimum 
at the middle of length and increasing toward the both ends. The piston is 
fixed to a piston rod 15, which is guided along the tubular rod 33 and 
secured to the lower arm 3 by a cushion member 32. Piston 13 is movable in 
the opposite directions from the middle of cylinder 13 or neutral position 
with a similar length of stroke, for example 11 mm. An O-ring 16 of thick 
rubber is disposed between cylinder 13 and piston 14. Top and bottom 
rubber rings 17 are disposed on the inner top and bottom surfaces of 
cylinder 13. 
The length of stroke is remarkably smaller than the maximum twistable 
amplitude of the ends of torsion bar 7, in order both supress the increase 
of roll-angle to the extent of having no uncomfortable effect and to 
absorb the deformation of the torsion bar when a wheel passes over raised 
or hollow places on the ordinary road. For example, in the case of a 
typical 1,300 Kg weight vehicle, an 11 mm stroke corresponds to a 0.7 
degree of roll-angle. In view of this, it will be understood that such 
stroke of piston 14 has no substantial effect upon the stabilizer-action 
which is needed during turning, because the vehicle has a roll-angle of 
from 5 degrees to 10 degrees when turning rapidly. The aforementioned 
stroke is mostly sufficient to relieve the stabilizing force when the 
vehicle travels on the ordinary road. Even if large raised and hollow 
places in the road cause the torsion bar to be vertically displaced and 
twisted, the stroke of the piston will absorb the deformation of the 
torsion bar and consequently reduce the stabilizing force, resulting in 
maintaining comfort. 
When lower arm 3 is caused to rise by a bump on a road, piston 14 moves 
upward from the neutral position, as seen in FIG. 4. Meanwhile, O-ring 16 
is rolled up and flatly compressed in a void space defined by a cylinder 
13 and piston 14. Thus, the resisting force against the movement of piston 
14 increases as the piston advances from the neutral position to the top 
end of cylinder 13. This is shown by the advance process line in the 
diagram of FIG. 5, in which are shown the characteristics of the 
reciprocal device for use with a typical 1,3000 Kg weight passenger car. 
The device has the following particulars; cylinder's taper angle of 4.5 
degrees, piston's taper angle of 4.5 degrees, chloroprene O-ring of 32 mm 
outer diameter, 6 mm cross-sectional diameter, and 70 degrees rubber 
hardness, with 1 mm initial compression at the neutral position. 
After the wheel has passed the bump, piston 14 returns to the neutral 
position. As shown by the return process line in the diagram of FIG. 5, 
there is no dynamical stability or resisting force in the return process. 
One cycle of the advance and return processes defines a closed area in the 
diagram, which corresponds to an absorption energy being effective to 
relieve the stabilizing action of the torsion bar and the rolling of the 
vehicle. When the wheel passes over a hole, the piston moves downward from 
the neutral position, so that the device performs the same action in the 
extensional stroke as the intensional stroke. 
For the purpose of enlarging the effective absorption energy, the force in 
the return process should be as small as possible. In preference, the 
taper angle of cylinder 13 and piston 14 is in a range of from 4 degrees 
to 5 degrees, because the dynamical stability is naught when the angle is 
less than 4 degrees and somewhat strong if the angle is larger than 6 
degrees. The device requires a small resisting force in the vicinity of 
the neutral position, otherwise free vibrations occur in the stabilizer to 
thereby reduce comfort. In view of the rolling rigidity, such a small 
resisting force is also required. The resisting force is zero when the 
piston is just in the neutral position but abruptly increases when it is 
apart even 1 mm from the neutral position, resulting in a smooth starting 
actuation. The abruptly standing force advantageously enlarges the 
enclosed area in the diagram, that is, the absorption energy. Therefore, 
the O-ring is so disposed at the neutral position as to be initially 
compressed under a certain pressure. The reciprocal device due to the 
characteristics as described above is capable of going into action by a 
small amplitude of the torsion bar produced by relatively small bumps and 
holes in a good road, resulting in a more comfortable ride. As the 
resisting force gradually increases toward the end of the stroke, the 
person feels less angular acceleration than the prior art, and the 
negligible resistance in the return stroke allows the piston to precisely 
return to the neutral position and decreases the roll or sway of the 
vehicle as compared to the prior art. 
Referring to FIG. 6, in which the second embodiment is shown, the 
reciprocal device 10a has the same piston 14 as in the first embodiment 
and a cylinder 13a, the stroke of which is so shortened to be equal to 
half the stroke of the previous one. Cylinder 13a has a solid rod 33a 
connected to the end 9 of torsion bar 7. Piston 14 has a piston rod 15a 
loosely passing through the cylinder 13a and connected to the lower arm 3. 
Piston rod 15a is angularly, somewhat freely movable in reference to 
cylinder 13a, so that the device 10a has the property of a free joint. 
Piston rod 15a needs no rod-guide, so that the second embodiment is so 
compact as to be suitable for use with a small size car, as compared with 
the known friction damper. 
Referring to FIG. 7, in which the third embodiment is shown, it has a 
couple of reciprocal ring devices 13b symmetrically disposed on the 
opposite sides of each end 9 of torsion bar 7 and a bolt assembly 24 
having the bottom end connected to the lower arm 3. The bolt assembly 24 
axially passes through the ring devices 13b and the end 9 of torsion bar 7 
to support the devices 13b from the both outsides. Each ring devices 13b 
includes a pair of top and bottom inner rings 22, outer ring 20 and a 
rubber ring 25 disposed on the bottom inner ring 22. The outer ring 20 is 
a split ring of spring steel and has the top and bottom inner surfaces 21 
thereof tapered for sliding engagement with the respective tapered outer 
surfaces 23 of the top and bottom inner rings 22. The surfaces 21, 23 are 
preferable to have a common taper angle of 17 degrees. Each device 13b has 
about 5 mm stroke to give the torsion bar 7 an effect of 10 mm stroke on 
the both sides from the neutral position. Outer ring 20 has the inner 
surface lined with tetrafluoro resin having carbon powder as a filler. The 
inner ring 22, made of aluminum alloy, has the outer surface 23 coated by 
wear-proof alumina film. The ring device 13b has a great difference in 
resisting force between the advance and return processes. The 
characteristics of the third embodiment is graphically similar to that in 
FIG. 5. 
From the foregoing, it will be seen that the apparatus of the invention 
resolves the disadvantages of the prior art, because it permits the 
rolling of the vehicle to not stepwise but gradually increase in the 
transient period without giving uncomfort to persons in the vehicle. The 
apparatus is more compact in size and simple in construction than the 
prior art and, therefore, suitable to even small size cars. The apparatus 
allows a strong stabilizer to be equipped without reducing the merit of 
the independent suspension system, resulting in many advantages, such as a 
good road-holding, a good straight-running performance, and a comfortable 
ride. In addition, the apparatus advantageously interrupts the 
transmission of vibrations and noises from unsprung parts of the vehicle 
to the spring parts as an intervention therebetween, otherwise the 
vibrations and noises rise from the tire to the frame along the stabilizer 
interconnecting both parts.