Title of Invention

TORSION BAR BASED FRONT SUSPENSION AND STEERABLE AXLE

Abstract 1) A torsion bar (4) for a suspension system of a vehicle, the torsion bar comprising: an anti-roll bar (4a, 4b), capable of being rotated along first axis A-A for suspending the torsion load exerted along the first axis A-A; two lower arms (4c, 4d, 4e), each attached through a revolute joint (4f) at each end of the anti-roll bar, the lower arm capable of being rotated along second axis B-B for suspending the torsion load exerted along the second axis B-B; mounting means (4g) for attaching each of the lower arm to a wheel spindle (3)
Full Text

Field of the Invention
The present invention in general relates to suspension system for a vehicle. In particular the present invention relates to a mechanical system, which has torsion bar as lower control arm of a suspension apart from its normal purpose of serving as anti-roll bar.
Background of the Invention
As it is commonly known, the primary fiinction of a suspension system is to:
Provide vertical compliance so the wheels can follow the uneven road, isolating the chassis from roughness in the road.
Maintain the wheels in the proper steer and camber attitudes to the road surface.
React to the control forces produced by the tires in longitudinal (acceleration and braking) forces, lateral (cornering) forces braking and driving torques.
Resist roll of the chassis.
Keep the tires in contact with the road with minimal load variations.
Focusing on the suspension systems currently being used in vehicles, the broader categories in which the suspension can be categorized are:
1. Dependent suspensions
2. Independent suspensions
The dependent suspensions include beam axles, kept in place by leaf springs and shock absorbers. The advantages of this include its simplicity, low cost, and rugged layout, as well as a naturally high roll center, which reduces

body, rolls in turns. This has disadvantages in its performance. A bump at one wheel will be transferred across to the other wheel. In addition, the gyroscopic forces of both wheels work together to induce shimmy, and the design results in greater unsprung weight and a rough ride.
The independent suspensions include McPherson strut, double wishbone, trailing-arm, or molten rubber suspension. These suspension systems are independent from each other except where it is joined by an anti-roll bar. These came into existence around 1930 and have been in use in one form or another pretty much ever since then.
The independent suspensions mainly consist of upper arm, lower arm, strut type spring and shock absorber or solid mass of rubber, with an anti-roll bar, which prevent the roll motion of the whole vehicle. Independent suspension typically offers better ride quality and handling characteristics, due to lower unsprung weight and the ability of each wheel to address the road undisturbed by activities of the other wheel on the vehicle. Independent suspension requires additional engineering effort and expense in development versus a live axle or beam axle arrangement.
Torsion bar springs is a bigger categorization in which the anti-roll bars can be classified. They are used in a wide range of installations from precision instruments through balance springs to automotive and military tank springs. This has disadvantages in terms of efficiency of material utilization, complexity, and production costs.
Suspension springs are generally loaded in one direction only and, they are usually shot peened and preset. The bar is subjected to both processes because this enables the springs to operate at high stresses required to them. Without shot-

peening and presetting, the bars would encounter early fatigue failures and would suffer excessive settling. These springs are categorized in different classes based on its applications and operating stress levels as shown in Table 1.
Stabilizer bars (classes 700 and 550 of torsion bars) are generally made to give a certain roll resistance, and the stress is of secondary consideration. As a stabilizer bar is a part of the suspension and is subjected to reverse loading, it should be shot peened if some areas are stressed in excess of 700 MPa, but it need only be shot peened in the highly stressed areas.
In a turn, the sprung mass of the vehicle's body rotates around its roll axis. The roll axis is a line that joins the front and rear roll centers. If the vertical distance between the roll axis and the center of gravity is not zero, a torque (roll moment) equal to the centrifugal force times the distance between the center of gravity and the roll axis will be exerted on the sprung mass, causing the body to lean towards the outside of the turn. This force is called the roll couple. One effect of body (frame) lean, for typical suspension geometry, is positive camber of the wheels on the outside of the turn and negative on the inside, which reduces their cornering grip (especially with cross ply tires).
Roll couple is resisted by the suspension's roll stiffness, which is a function of the spring rate of the vehicle's springs and of the anti-roll bars, if any. The use of anti-roll bars allows designers to reduce body lean without making the suspension's springs stiffer in the vertical plane, which allows improved body control with less compromise of ride quality.
The spring rate of an anti-roll bar is based on the fourth power of the torsion bar's diameter, the stiffiiess of the material, the inverse of the length of the lever arms (i.e., the shorter the lever arm, the stiffer the bar), the geometry of the

mounting points, and the rigidity of the bar's mounting points. Some anti-roll bars, particularly those intended for use in auto racing, are adjustable, allowing their stiffiiess to be altered by increasing or reducing the length of the lever arms. This permits the roll stiffness to be tuned for different situations without replacing the entire bar.
One of the functions performed by the anti roll bars is the reduction of body lean. The reduction of body lean is dependent on the total roll stiffness of the vehicle. Increasing the total roll stiffiiess of a vehicle does not change the steady state total load (weight) transfer from the inside wheels to the outside wheels. It will only reduce body lean. The total lateral load transfer is determined by the CG height and track width.
The other function of anti roll bars is to tune the high g force / limit understeer behavior of the vehicle. The limit understeer behavior is tuned by changing the proportion of the total roll stiffiiess that comes from the front and rear axles. Increasing the proportion of roll stiffiiess at the front will increase the proportion of the total weight transfer that the front axle reacts and decrease the proportion that the rear axle reacts. This will cause the outer front wheel to run at a higher slip angle, and the outer rear wheel to run at a lower slip angle, which is an understeer effect. Increasing the proportion of roll stiffness at the rear axle will have the opposite effect and decrease understeer.
Many vehicles utilize stabilizer (anti-roll) bars to increase roll rate for satisfactory handling characteristics. Stabilizer bars are laterally mounted torsional springs, which resist vertical displacement of the wheels relative to one another. Vertical suspension rates are not increased when both wheels are deflected simultaneously; however, stiffiiess is increased for one wheel bump. Passenger car suspensions, tuned to give a soft ride with low rate springs, use stabilizer bars to

reduce vehicle roll with only a minor deterioration of ride. Motor homes and pick┬Čup trucks with slide in campers employ stabilizer bars to control body roll caused by a high center of gravity. Stabilizer bars are generally installed in both front and rear suspensions or in front suspensions only. Use of stabilizer bar on the rear suspension alone, can sometimes have an adverse effect on vehicle handling. Such installations should be tested under severe cornering conditions to ensure the desired handling characteristics.
Stabilizer bars are generally one piece with bends to provide arms and meet package constraints. Stabilizer bars consisting of a torsion bar and separate arms are used on race cars and experimental vehicles. Bar diameter is easily changed to determine optimum roll rates.
Materials and processing requirements of stabilizer bars are identical to regular torsion bar springs with the exception that stabilizer bars are not preset. Attachments to frame and suspension components are usually rubber insulated. Care must be taken in locating attachment points to avoid interface with suspension motion unless a specific constraint is required.
The total suspension roll rate is due in part to the suspension springs and in part to the stabilizer. When connected to a rigid axle suspension, the roll rate of the stabilizer bars equals its effective roll rate at the wheels. When applied to an independent suspension. However, the bar roll rate is greater than its effective roll rate at the wheels. The required bar roll rate can be obtained by multiplying the desired effective roll rate at the wheels by the square of the ratio of wheel travel to bar travel at the bar end, and by the square of the ratio of bar length to wheel tread.
When rubber supports are used, as is usually the case, they will add considerable deflection and thereby reduce the calculated roll rate of the bar. Any

connecting links with rubber joints will add to the reduction of roll resistance in the critical stages of initial roll motion. Usually the roll rate of the steel bar is reduced 15-30% by rubber deflections.
The overall configuration of the stabilizer bar, and the points of attachment to the suspension and vehicle structure are usually determined by layout from available space in the vehicle. With the configuration defined, a bar diameter can be found which will provide the desired roll rate.
The advent of lighter vehicles developed to achieve better fuel economy to classify them in a lower weight class has provided an opportunity to utilize tubular stabilizer bars in some vehicle models. Tubular bars can be 35-50% lighter than equivalent rate solid bars.
The penalties for a weight saving torsional equivalent tubular bar apart from product cost are those of increased outside diameter, higher stresses, lower fatigue life.
The higher stresses in the tubular bar, which usually occur at the main bend outside the inner bushing from the bar end, are higher because of the necessary larger diameter of the tubular bar over an equivalent rate solid bar and because of meridional or circumferential stress.
The meridional stress is an additional stress not found in solid diameter stabilizer bars because the cross-section of the tubular bar can be elastically deformed with loading.
The following comparison of tubular to solid stabilizer bars with the same torsional rate outlines their differences:

The tubular bar is lighter
The tubular bar has a larger outside diameter
As the outside diameter of the tubular bar is increased the wall thickness is decreased
Tubular bar stresses (bending and torsional shear) are higher than in an equivalent solid bar
There is an additional stress (circumferential or meridional) in the main bends of the tubular bars.
Generally, the effect of increased stresses in equivalent tubular bars can be reduced by utilizing the following criteria: larger wall thickness, larger bend radii, and shot peening of major bends (areas of high operational stresses).
Summary of the Invention
It is an object of the present invention to provide a torsion bar for a suspension system of a vehicle in order to overcome the disadvantages of the conventional suspension systems. The present torsion bar comprises an anti-roll bar capable of being rotated along first axis for suspending the torsion load exerted along the first axis; two lower arms each attached through a revolute joint at each end of the anti-roll bar, the lower arm capable of being rotated along second axis for suspending the torsion load exerted along the second axis; mounting means for attaching each of the lower arm to a wheel spindle.
The concept of torsion bar based suspension system is applicable to suspension for vehicles, for example light commercial vehicles, SUVs and passenger segment.

The present invention does not have a lower arm and an anti-roll bar separately.
The torsion bar described here has different sections. These sections are to be made in manner to make the torsion bar work as desired. This torsion bar has two axes of rotation namely first axis and the second axis about which it undergoes torsion thereby providing combined suspension of the lower arm and the anti-roll bar for the vehicle. The angle between the two axes will determine the roll characteristics of the suspension while working as the anti-roll bar and the ride as well as handling characteristics while working as the lower arm of the independent suspension.
This combination of two purposes being served by the same torsion bar reduces the number of parts in the suspension system thereby improving ride comfort when. Apart from this the load on the vehicle comes on this suspension system.
It is an other object of the present invention to provide suspension system for a vehicle, the suspension system comprises a torsion bar; two side link, one side link attached on left end and the other side link attached on the right end of the torsion bar; a tie bar, attached to the right end and left end of the torsion bar by the side links; two wheel spindle, one wheel spindle attached in left end and the other wheel spindle attached in the right end of the torsion bar by ball and socket joint; two wheel, one wheel attached to the left side wheel spindle and the other wheel attached to the right side wheel spindle; two tie rod, one tie rod attached to the left side wheel spindle and the other tie rod attached to the right side wheel spindle; a rack, attached to free ends of the tie rod, the other end of the tie rod being attached to the left side wheel spindle and right side wheel spindle; two upper arm, one upper arm attached to the left side wheel spindle and the other

upper arm attached to the right side wheel spindle; chassis, with its left end attached to the upper arm on the left side and its right end attached to the upper arm on the right side; two shock absorber one shock absorber attached to the left side of the torsion bar by the side link and the other shock absorber attached to the right side of the torsion bar by the side link; two locating struts, one locating strut attached to the shock absorber and the upper arm in the left side and the other locating strut attached to the shock absorber and the upper arm in the right side;
The locating strut controls the motion of the torsion bar in the horizontal and the vertical direction.
Brief description of the drawings
The present invention is described by means of the following drawings and table:
Figure 1: Illustrates torsion bar of the present invention.
Figure 2: Illustrates torsion bar based suspension system according to the
present invention. Figure 3: Illustrates Half section isometric view of the present invention. Figure 4: Illustrates different components of the present invention (1) Upper
arm, (2) Link, (3) Wheel spindle, (4) Shock absorber, (5) tie-bar and
(6) locating strut. Figure 5: Illustrates the conventional Anti-roll bar arrangement in independent
suspensions.
Table 1: Shows operating stresses and applications of different class of suspension springs.

Detailed description of the drawings
Figure 1 illustrates torsion bar of the present invention.
This torsion bar (4) has two axes of rotation the first axis being A-A and second axis being B-B as illustrated in Figure 1, about which it undergoes torsion thereby providing combined suspension of the lower arm and the anti-roll bar for the vehicle.
Torsion bar (4) has different portions as illustrated in Figure 1. The torsion bar comprises an anti-roll bar (4a, 4b), capable of being rotated along first axis A-A for suspending the torsion load exerted along the first axis A-A; two lower arms (4c, 4d, 4e), each attached through a revolute joint (4f) at each end of the anti-roll bar, the lower arm capable of being rotated along second axis B-B for suspending the torsion load exerted along the second axis B-B; mounting means (4g) for attaching each of the lower arm to a wheel spindle (3).
The angle between the two axes A-A and B-B determines the roll characteristics of the suspension while working as the anti-roll bar and the ride as well as handling characteristics while working as the pseudo lower arm of the independent suspension.
The torsion bar (4) is connected to the wheel spindle (3L) by a ball and socket joint at the attachment point 4g as illustrated in Figure 1. The torsion bar (4) is connected to the chassis (1) along the portion 4a as illustrated in Figure 1 through a revolute joint. The portion 4h illustrated in Figure 1 is a protrusion of the torsion bar (4) to give attachment points to the link (IIL) which supports the shock absorber (6L), the locating strut (7L) and also tie-bar (10), as illustrated in Figure 1. The torsion bar (4) has three bends; first bend depicted by portion 4b

second bend between portions 4c and 4d and the third bend between portion 4d and 4e as illustrated in Figure 1. The end of the torsion bar (4) is depicted by the portion 4e and this portion again is attached to the same bar around the portion 4c by the revolute joint illustrated as 4f in Figure I.
The shock absorber (6L, 6R) provides the damping characteristics to the conceptual torsion bar (4) and the locating stmt (7L, 7R) will provide a definite path of travel to the torsion bar (4). The link (1IL, IIR) is connected to the torsion bar (4) through ball and socket joint. This joint will help in lateral stability of the whole structure.
The attachments points on the shock absorber 6a and the locating strut 7a are connected to chassis (1). Furthermore the upper arm (5) is the strength-providing member and hence it is heavy.
The present invention of the torsion bar (4) to work as lower arm for the independent suspension system is mainly due to the shape of the torsion bar (4). The shape of the torsion bar (4) consists of various portions as can be seen in the Figure 1. The features, which make it suitable for working as a lower arm, are:
a. Bend between portion 4c and 4d as illustrated in Figure 1 where the
torsion bar undergoes torsion around the axis B-B as illustrated in the Figure 1
b. The revolute joint shown as 4f in Figure 1, which connects the
portion 4e with portion 4c as illustrated in Figure 1
This present invention of torsion bar (4) to work as an anti-roll bar is accomplished by allowing torsion to move in an axis of rotation A-A as illustrated in Figure 1. The portion 4b of the torsion bar undergoes torsion thereby allowing rotation of portion 4c with respect to portion 4a as illustrated in Figure 1, and the portion 4a can rotate with respect to the chassis (1), as a revolute joint is present

between them. As Figure 3 shows a half section of the proposed torsion bar (4), a complete torsion bar will act as an anti-roll bar thereby preventing the relative travel of the left and the right wheels on the fi-ont.
Figure 2 illustrates the torsion bar based suspension system.
Wheel (2L) is connected to wheel spindle (3L) by a revolute joint at wheel spindle attachment point 3b illustrated in Figure 4(3). Wheel spindle (3L) is connected to the upper arm (5L) through the attachments point 3c and 3a illustrated in Figure 4(3) by a ball and socket joint. The upper arm (5L) is connected to the chassis (1) by revolute joints at 3a and 3b as illustrated in Figure 4(3). The tie rod (8L) is connected to the wheel spindle (3L) by portion 3c as illustrated in Figure 4 (3) by a revolute joint and at the other end it is connected to the rack (9) by a revolute joint. The tie rod (8L, 8R) and the rack (9) are the steering linkages. The link (IIL) is connected to the shock absorber (6L) and the locating strut (7L) by a revolute joint 3a and 3c as illustrated in Figure 4 (3). The tie-bar (10) is a connection link between the left and the right side link (1IL, 11R). A tie-bar (10) is an alloy/steel bar that increases chassis rigidity by bracing the left and right pseudo lower-control-arm as a part of torsion bar (4). It is made to reduce the non-pivoting movement of the control arms and to stiffen the sub-frame to lessen the distortion of the lower suspension, especially during hard cornering. As a result, it improves the handling and steering response of the vehicle much like a strut bar.





WE CLAIM :
1) A torsion bar (4) for a suspension system of a vehicle, the torsion bar
comprising:
an anti-roll bar (4a, 4b), capable of being rotated along first axis A-A for
suspending the torsion load exerted along the first axis A-A;
two lower arms (4c, 4d, 4e), each attached through a revolute joint (4f) at
each end of the anti-roll bar, the lower arm capable of being rotated along
second axis B-B for suspending the torsion load exerted along the second
axis B-B;
mounting means (4g) for attaching each of the lower arm to a wheel spindle
(3).
2) The torsion bar as claimed in claim 1, comprising:
a tie bar (10) for connecting both side links (1IL, 1IR) one present on the left side of the torsion bar and the other present on the right side of the torsion bar thereby acting as a pseudo lower control arm for handling and steering response.
3) The torsion bar as claimed in claim 1, wherein the angel between the first axis A-A and second axis B-B determines the roll characteristics of the suspension while working as the anti-roll bar and the ride as well as handling characteristics while working as the pseudo lower arm of the suspension.
4) The torsion bar as claimed in claim 1, wherein the lower arm (4c, 4d, 4e) is attached to wheel spindle (3L, 3R) along the second axis of rotation B-B.

5) The torsion bar as claimed in claim 1, wherein the anti-roll bar (4a, 4b) is attached to chassis (1) along the first axis of rotation A-A.
6) The torsion bar as claimed in claim 1 wherein the lower arm (4c, 4d, 4e) is steerable in left direction and in right direction.
7) A suspension system for a vehicle, the suspension system comprising:
a torsion bar (4);
two side link (UL, IIR), one side link (IIL) attached on left end and the
other side link (1IR) attached on the right end of the torsion bar;
a tie bar (10), attached to the right end and left end of the torsion bar by the
side links (11);
two wheel spindle (3L, 3R), one wheel spindle (3L) attached in left end and
the other wheel spindle (3R) attached in the right end of the torsion bar by
ball and socket joint;
two wheel (2L, 2R), one wheel (2L) attached to the left side wheel spindle
and the other wheel (2R) attached to the right side wheel spindle;
two tie rod (8L, 8R), one tie rod (8L) attached to the left side wheel spindle
and the other tie rod (8R) attached to the right side wheel spindle;
a rack (9), attached to fi-ee ends of the tie rod, the other end of the tie rod
being attached to the left side wheel spindle and right side wheel spindle;
two upper arm (5L, 5R) one upper arm (5L) attached to the left side wheel
spindle and the other upper arm (5R) attached to the right side wheel
spindle;
chassis (1), with its left end attached to the upper arm on the left side and
its right end attached to the upper arm on the right side;

I
two shock absorber (6L, 6R), one shock absorber (6L) attached to the left
side of the torsion bar by the side link and the other shock absorber (6R)
attached to the right side of the torsion bar by the side link;
two locating strut (7L, 7R), one locating strut (7L) attached to the shock
absorber and the upper arm in the left side and the other locating strut (7R)
attached to the shock absorber and the upper arm in the right side; wherein
the torsion bar comprising:
an anti-roll bar (4a, 4b), capable of being rotated along first axis A-A for
suspending the torsion load exerted along the first axis A-A;
two lower arm (4c, 4d, 4e), each attached through a revolute joint (4f) at
each end of the anti-roll bar, the lower arm capable of being rotated along
second axis B-B for suspending the torsion load exerted along the second
axis B-B;
mounting means (4g) for attaching each of the lower arm to a wheel spindle
(3).
8) The suspension system as claimed in claim 1 wherein the locating strut (7L, 7R) controls the motion of the torsion bar in the horizontal and the vertical direction.


Documents:

1301-CHE-2007 AMENDED PAGES OF SPECIFICATION 06-09-2013.pdf

1301-CHE-2007 AMENDED CLAIMS 06-09-2013.pdf

1301-CHE-2007 EXAMINATION REPORT REPLY RECEIVED 06-09-2013.pdf

1301-che-2007 claims.pdf

1301-che-2007 description(complete).pdf

1301-che-2007 drawings.pdf

1301-che-2007 form-26.pdf

1301-che-2007-correspondnece-others.pdf

1301-che-2007-description(provisional).pdf

1301-che-2007-drawings.pdf

1301-che-2007-form 1.pdf

1301-che-2007-form 3.pdf


Patent Number 257730
Indian Patent Application Number 1301/CHE/2007
PG Journal Number 44/2013
Publication Date 01-Nov-2013
Grant Date 30-Oct-2013
Date of Filing 22-Jun-2007
Name of Patentee ASHOK LEYLAND LIMITED
Applicant Address 19 RAJAJI SALAI, CHENNAI 600001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 SATHYA PRASAD MANGALARAMANAN c/o ASHOK LEYLAND LTD, KHIVRAJ COMPLEX, BLDG 2-(FIRST FLOOR), 477-482 ANNA SALAI NANDANAM, CHENNAI 600 035, INDIA.
PCT International Classification Number B60G9/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA