ELASTOMERIC SANDWICH SPRING STEERING STABILIZER

FIELD OF INVENTION

The present invention relates to a self-steer lift axle for medium and heavy duty vehicles. More particularly relates to an elastomeric sandwich spring steering stabilizer with or without a coil spring actuator for the self-steer lift axle.

BACKGROUND OF THE INVENTION

Self-steer lift axle system (1) is commonly used in medium and heavy duty trucks, trailers and multi axle coach to extend the tire life by reducing tire scrubs and wear. The self steer lift axle (1) is made self steering by adjusting caster angle of the wheels so that the drag of the wheels as the vehicle moves in the forward direction. Therefore, the suspension system including wheel assembly steers automatically in response to the steering of the front axle of the vehicle. If a lift axle mechanism attached with the self-steer axle system (1), the axle beam (2) can be lifted-off the road surface when the vehicle is operated unladen and partially loaded conditions, therefore it is called as self steer lift axle suspension.

FIG.1 shows a conventional assembly view of the self-steer lift axle suspension system (1). The self steer-ability of the axle is controlled by a pair of steering dampers (4) which are mounted in between the bottom air bellows mounting bracket(3) and the track rod lever (7) of the self-steer lift axle(l). In addition, it dampens oscillations caused by road undulates or debris. In general, the steering dampers (4) are conventional shock absorber (5) with or without an external open coil spring (6). The system is commonly called as coil over steering damper (4) or steering stabilizer (4).

The steering damper (4) has a hydraulic cylinder, in which an incompressible hydraulic fluid is filled. The hydraulic cylinder is separated into two chambers by a piston. The piston has a small orifice which allows the fluid from one chamber to other chamber. The piston also has a seal at its head. It doesn't allow the fluid from one chamber to other chamber. The piston slides in side of the hydraulic cylinder when the vehicle is operated. One end of the steering stabilizer (4) is attached with the track rod lever (7) of the axle (2) and the other end of the steering stabilizer (4) is connected to the axle beam or suspension's structure of the vehicle, preferably the bottom air bellow mounting bracket (3). When the piston slides inside of the hydraulic cylinder, the fluid can pass from one chamber to other chamber through the small orifice only. As the orifice restricts the flow of the hydraulic fluid in between the two chambers, oscillations experienced in the wheel assembly (9) due to road shock and wheel shimmy are appropriately dampened and the tracking is also stabilized. Thereby, the self steer-ability of the self steer lift axle (1) is controlled. The open coil spring (6), having an appropriate stiffness, is provided for self-centering characteristic feature of the wheel assembly (9).

In the steering stabilizer (4), few frequent failures are observed. More often, the seals, which are provided in the piston and both the ends of the hydraulic cylinder, get fail; therefore, it leads hydraulic fluid leakage in the shock absorber (5). The piston rod is frequently buckled due to shock load caused by severe cornering force. In addition, the steering stabilizer (4), is subjected to damage due to road undulates. These all the drawbacks lead to high maintenance in the self steer lift axle (1). In addition, the cost of the coil over spring type steering stabilizer (4) is also high.

In order to, address the above mentioned drawbacks which are found in the commercially available coil over steering stabilizer (4), a rotary type steering stabilizer is invented as disclosed in US patent No's: 7766349B2 and7360773 B3. The rotary type steering stabilizer is used to control the steer-ability of the self- steer axle (1). It is basically a twist type rubber spring which constitutes a rotary stabilizer. It acts directly about the king pin of the axle (2) of the vehicle. The rotary stabilizer is co-axially aligned with the kingpin centerline (8). Alternatively, the rotary stabilizer may be mounted and co-axially aligned with a pivot joint (10) associated with a track rod lever (7). The rotary type steering stabilizer may also have a self-centering mechanism which is incorporated therein. In addition, it is mounted to above the axle (2) in the position where it is less likely to be experienced to road undulates. However, the rotary stabilizer is subjected to a large tortional load (i.e., twisting load) as it the twist type rubber spring. Therefore, the rubber is subjected to a sever shear stress and less axial compressive stress. The rotary type rubber springs (i.e. rubber bush) are commonly used to reduce shock load in the leaf spring suspension's eye end and suspensions control arm's eye end. Practically, a frequent rubber bush failure is observed in the suspension due to enormous shear stress developed in the rubber spring when it is especially subjected to a high twisting torque (i.e., twisting moment). Therefore, such type of the rubber spring leads to a high maintenance and a less reliability.

The helical coil springs (6) of the steering stabilizer (4) is used to provide a force to the wheel assembly which is required to maintain the wheel assembly in neutral position. The helical coil springs (6) are used in the self steer lift axle (1) to exert a force, provide flexibility, and store or absorb energy. In the self steer lift axle (1), the helical coil springs (6) are continuously subjected to a cyclic load (i.e., compression and extension force) when the vehicle is operated. It leads to fatigue failure of the spring. In addition, the helical coil springs (6) are also continuously subjected to a constant compressive force when the vehicle is not operated. Therefore, the helical coil springs (6) tend to creep failure (i.e., spring relaxation or permanent set). Due to the above mentioned reasons, the helical coil springs (6) of the steering stabilizer (4) fail to provide flexibility and store or absorb energy. It leads to wheel shimmy and oscillation in the wheel assembly (9). In addition, coil spring (6) fails to maintain the wheel assembly in straight ahead position (i.e., fails to retain to straight ahead position). Such phenomenon is observed in the commercial available self steer lift axle (1). Therefore, the wheel assembly (9) is in turned position after lifting the axle (2).

In addition, the coil over spring steering damper (4) itself consumes much time to assemble during assembling the self steering axle (I); because, the coil over spring steering damper (4) should be compressed to a desired length by applying a large force before connecting the steering stabilizer (4) in between the tract rod lever (7) and the bottom air bellow mounting bracket (3) (i.e., axle beam or suspension structure).

In view of the above, there is a need for a relatively low cost, light weight and compact steering stabilizer. The steering stabilizer should be designed such a way that it should have less number of parts, light weight and easy to assembly feature. In addition, it requires relatively little maintenance and it should be maintained easily. The present invention addresses the above mentioned drawbacks which are found in the commercially available self steer lift axle (1).

OBJETIVES OF THE INVENTION

A principal object of the present invention is to provide an elastomeric sandwich spring steering stabilizer for the self steer-lift axle which is particularly for control the self steer-ability of the axle.

Another objective of the present invention is to provide a steering stabilizer which should be mounted easily to the steering linkage of the axle beam.

Yet another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should have fewer parts.

Another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should have little maintenance and high reliability.

Another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should be inexpensive and easily maintainable.

Another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should be ease to assemble to the axle components.

Another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should be lightweight.

Another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should have no rotating parts.

Another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which should work properly even in rapid operation.

Yet another objective of the present invention is to provide a steering stabilizer for the self steer lift axle which absorbs road shock and reduce oscillation.

An objective of the present invention is to provide a steering stabilizer which reduces shimmy.

Another objective of the present invention is to provide a steering stabilizer which should be easily manufactured.

Another objective of the present invention is to provide a steering stabilizer which should give better life than coil spring steering stabilizer.

SUMMARY OF THE INVENTION

The present invention provides a simple elastomeric sandwich spring steering stabilizer with or without a coil spring actuator for the self-steer lift axle. It controls the steer-ability of the self-steer lift axle suspension. The elastomeric sandwich spring steering stabilizer comprises a plurality of elastomeric pads, plurality of steel plates and plurality of blind nuts. The blind nuts are immersed in the elastomeric pads. The elastomeric pad is preferably made of rubber or polyurethane. The blind nuts are used to connect the elastomeric sandwich spring with the track rod and the bottom air bellow mounting bracket. The elastomeric pads are laminated with the steel plates having appropriate thickness. The elastomeric sandwich springs are connected in between the steering linkage and axle beam structure of the self steer- lift axle; especially, in between steering rod lever and the bottom air bellow mounting bracket. The elastomeric sandwich spring, having an appropriate stiffness, restricts the abrupt lateral motion (i.e., lateral velocity) of the wheel assembly when the vehicle is operated.

In order to achieve required load and deflection curve, a special attention is given in design and position of the elastomeric sandwich spring steering stabilizer in the self steer lift axle. The stabilizer is positioned in the axle such that compressive stress developed is higher than the shear stress developed in the elastomeric sandwich spring.

As the elastomeric sandwich spring has an appropriate stiffness with an ability to store or absorb the energy, it is sufficient to control the self steer-ability of the self steer lift axle. However, to achieve variable the self steer-ability of the self steer lift axle, a pair of coil spring actuators may also be included to the elastomeric sandwich spring stabilizer.

The coil spring actuator consists of a pair of spring seats, a helical coil spring with or without a sandwich rubber spring, a bearing bush, a push rod having round concave shape at its one end, and a pair of steering rods. The coil spring actuator is connected with the suspension structure preferably with the bottom air bellow mounting bracket. The coil spring actuator may be made of open helical coil spring with or without a sandwich rubber spring to achieve required linear or non linear stiffness characteristic (i.e., load and deflection curve). The selection of the size of coil spring and the sandwich rubber spring is decided on the basic of nature of stiffness (i.e., linear or non linear stiffness characteristic) required for the particular load carrying capacity of the self steer lift axle. The coil spring actuator is directly secured to the mounting bracket connected to the axle through mechanical means. The bearing bush is made of nylon coated steel bush forcefully inserted to the boss provided in the bottom air bellows mounting bracket. The push rod, having round concave shape at its one end, is attached to the spring seat by mechanical means.

The steering arm having appropriate length and round shape in its forefront end, is connected to the threaded portion of the wheel where the steering rod is commonly connected. Similar one more arrangement is also connected in the other side of the wheel assembly. The push rod of the coil spring actuator pushes the steering lever attached to the wheel of the axle, so that the wheel tends to align to the neutral position due to tortional moment generated in the kingpin of the axle. If the coil spring actuator is used to provide sufficient flexibility with an appropriate stiffness to the self steer lift axle.

The elastomeric sandwich steering stabilizer with or without coil spring actuator mechanism dampens oscillations which is caused by wheel shimmy and road shock due to road irregularities; thereby the tracking is stabilized.

If the vehicle moves straight forward motion, the coil spring actuator system does not experience any load, whereas, if the vehicle moved in a curved path, the coil spring gets compressed and gives a counter and opposite force to the steering lever to align the wheel assembly to the natural position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is view of the self steer lift axle assembly in accordance with the prior art.

FIG. 2 shows schematic of the elastomeric sandwich spring steering stabilizer with coil spring mechanism in accordance with the present invention.

FIG. 3 shows schematic of the elastomeric sandwich spring of Fig 2.

FIG.4 shows a typical load-deflection curve of the elastomeric sandwich spring of Fig 2.

FIG. 5 shows a coil spring actuator of Fig 2

FIG.6 is a view of self steering lever.

DETAILED DESCRIBTION OF THE INVENTION

The present invention relatives to an elastomeric sandwich spring steering stabilizer (11) for the self-steer lift axle (1), which dampens the road shocks and oscillations caused by the road undulates and maintains the wheel assembly (9) in a neutral position when the vehicle is operated.

FIG.2 shows the schematic of the elastomeric sandwich spring steering stabilizer (11) of the present invention with coil springs actuators (12). The steering stabilizer (11), described herein, comprises of a pair of elastomeric sandwich springs (17), a pair of coil spring actuators (12) and a pair of steering levers (14). Coil spring actuators (12) and steering levers (14) may be included to the steering stabilizer (11) to achieve various stiffness rates for the self steer lift axle (I). Elastomeric sandwich springs (11) are located in between the track rod lever (7) and the bottom air bellows bracket (3) at the both the ends of a self steer lift axle. The coil spring actuator mechanism (12) comprises of an open helical coil spring (15) with or without a sandwich rubber spring (16) as shown in Fig.5. The helical coil spring (15) with or without a sandwich rubber spring (16) actuators are attached to both the side (LH and RH) of bottom air bellow mounting brackets (3). Steering levers (14) are attached in the locations where the steering rod of the axle beam (2) is commonly connected to the wheel assembly (9).

FIG. 3 shows the schematic of the elastomeric sandwich spring (11). It comprises a plurality of elastomeric pads (17), plurality of steel plates (18) and plurality of mounting blind nuts (19). The elastomeric pad (17) is preferably made of rubber or polyurethane. The elastomeric pad (17) is interlaid (laminated) with the steel plates (18) of appropriated thickness. Blind nuts (19) are immersed in the elastomeric pads (17) and are used to secure with the bottom air bellow mounting brackets (3). A hole (20) is provided in the middle; so that the elastomeric sandwich spring (11) is to accomplish more stable than a solid, spring.

FIG.4 shows the load deflection curve of the elastomeric sandwich spring (11)- A special attention is given to the design of the elastomeric sandwich spring (11) and position of the spring in the axle beam (2). The intermediate steel plates (18) are positioned in the spring (1 l)such that compression stress is only developed in the spring (1 l).For that, the center of pressure of the various layers lies on the center line (21) of the spring (i.e., geometric centers of the layers of the rubber). However, in order to maintain a linear resultant load if required, the structure of the spring (11) is designed and positioned in the axle beam (2) with a required offset such that a small amount of shear stress is also developed along with the compressive stress. Thereby, the resultant load is in straight line when the elastomeric sandwich spring (11) is loaded. That is the elastomeric sandwich spring (11) may be positioned in off-set in between the axle beam (2) and track rod lever (7), so that the compression stress developed in the spring is higher than the shear stress developed.

FIG. 5 shows the schematic of the coil spring actuator mechanism (12) using coil springs (15) with or without a sandwich rubber spring (16). The coil spring actuator comprises a helical coil spring (15) with or without a sandwich rubber spring (16), a push rod (22), a pair of spring seats (23), a push rod bearing bush and a lock nut (25). The coil spring (15) with or without the sandwich rubber spring (16) is located in between the spring seats (23) without pre-compression load. One end of the spring seats (23) is connected to the push rod (22) having round concave shape (13) at one end. The coil spring actuator assembly (12) is secured to the bottom air bellow mounting bracket (3) of the self steer lift axle (1) by the lock nut (25). When the vehicle is operated, the push rod (22) slides in a nylon coated bearing bush (24) which is forcefully tightened (i.e., fitted) to the boss (25) provided in the bottom air bellow mounting bracket (3). As the helical coil (15) is experienced load (i.e., compressive load), only when the vehicle is turned otherwise the helical coil (15) is in its original free height. In the present embodiment, continuous load in the helical spring (15) is avoided. Therefore the creep (i.e., permanent set) failure in the helical coil spring (15) is considerably reduced. Thereby, the self-steerable characteristic of the self steer lift axle (1) and reliability of the system are maintained for a required (i.e., desired) period by using the present invention. In addition, the assembly time of the steering stabilizer (11) is reduced as the coil springs (15) are mounted without pre- compression load.

FIG. 6 shows the view of steering lever (14). It is attached to the wheel assembly (9) in the location where the steering rod is usually mounted in the wheel assembly (9). Therefore, no modification is required in the wheel assembly (9) to mount the steering lever (14). A special attention is given to fabricate the steering lever (14). Especially, at the end of the steering lever (14), a simple round shape head (27) is provided which is mainly to keep a suitable contact preferably a point contact with the push rod ends (24) to reduce the rubbing action. The push rod (22) ends engages to the steering lever (14), when the vehicle is operated, and gives a force to turn the wheel assembly (9) to the neutral position.

The elastomeric sandwich spring steering stabilizer (11) especially maintains a desired cornering performance criteria (i.e., cornering stiffiiess) of the self steered lift axle (1). The elastomeric sandwich spring steering stabilizer (11) reduces down the oscillations (caused by wheel shimmy and road shock due to road irregularities) experienced in the wheel assembly (9) during vehicle operation; thereby, tracking is stabilized.

When the vehicle is operated, the self steer lift axle (1) is subjected to cornering force, acceleration force and braking force. When the vehicle gets turning, the steering levers (14) along with the wheel assembly (9) are turned with respect to the kingpin (8) of the axle beam (2). Therefore, the steering lever (14) is engages to the push rod (22) of the coil spring actuators (12) fitted in other side of the axle beam (2). The elastomeric sandwich spring steering stabilizer (11) with the coil spring actuator mechanism (12) gives a counter and opposite force to the wheel assembly (9) to maintain the wheel assembly (9) in the neutral position. For example, if the wheel assembly (9) is turned to the left direction, as viewed in the drawing, the RH side coil spring (15) is compressed. Therefore, wheel assembly (9) trends to turn to the neutral forward direction. Conversely, if the wheel assembly (9) is turned to the right side, as viewed in the drawing, the LH side coil spring (15) is compressed which trends to turn to a neutral forward direction. Further, when the vehicle is operated, the control of the axle beam (2) tends to maintain each of the steer-able wheels in the forward neutral position, due to the action of the elastomeric sandwich springs (11) and coil springs actuator mechanism (12).

A person, who has skill in design of mechanical system, would perform many modifications, additions, deletions of few components. In addition, some changes may be made to these specific embodiments, for example; simply changing the helical coil spring actuator (15) to conical coil spring actuator or pneumatic actuators, etc., and such modifications are contemplated by the principle of the present invention. Accordingly the forgoing detailed description is clearly understood that the present invention is presented by way of illustration and example only. The spirit and scope of the present invention is being limited solely by the appended claims and their equivalents.

WE CLAIM :

1. A steering stabilizing apparatus for a vehicle comprises:

a pair of elastomeric sandwich springs (11) arranged in between a track rod lever (7) and bottom air bellow mounting bracket (3) (i.e., axle beam) at the both the ends of a self steer lift axle; with or without

a pair of coil spring actuators (12) secured to bottom air below mounting brackets (3) at both the ends of the self steer lift axle (1).

2. The steering stabilizer according to the claim I, wherein said stabilizer comprises a pair of steering levers (14) attached to the both sides of the self steer lift axle (1)

3. The steering stabilizer according to the claim 1, where in said stabilizer comprises a plurality of steel plates, a plurality of elastomeric pads laminated with said steel plates and a plurality of blind nuts immersed in said elastomeric pads.

4. The steering stabilizer according to the claim 2, wherein said elastomeric pads are preferably made of rubber.

5. The steering stabilizer according to the claim 2, wherein said elastomeric pads are preferably made of polyurethane.

6. The steering stabilizer according to the claim 1, wherein said spring (13) is secured in between the track rod lever (7) and the bottom air below mounting bracket (3) of the self steer lift axle (1) by using mechanical means.

7. The steering stabilizer according to the claim 1, wherein said spring (13) has a hole (20) at middle to accomplish more stable than a solid spring.

8. The steering stabilizer according to the claim 1. wherein each one of the coil spring actuators (12) comprisesa helical coil springs (15) with or without a sandwich rubber spring (16),

a pair of spring seats (23);

a bearing bush (24), a push rod (22), and a loch nut (25).

9. The steering stabilizer according to the claim 8, wherein the bearing bush (24) is forcibly inserted to the boss (26) provided in bottom air bellows mounting brackets (3).

10. The steering stabilizer according to the claim8, wherein the push rod (22) ends having round concave shape (13) and secured to the spring seat (23).

11. The steering stabilizer according to the claim8, wherein the helical coil spring (15) with or without the sandwich rubber spring (16) is placed in between the spring seats (23).

12. The steering stabilizer according to the claim8, wherein the bearing bush (24) is preferably made of nylon coated steel in which the push rod (22) slides when the vehicle is operated.

13. The steering stabilizer according to the claim8, the steering lever (14) having round shape (27) at its end connected to the wheel assembly (9) of the self steer lift axle (1) by means of bolted screws, at a location where a steering rod is mounted in the wheeling assembly.

14. The steering stabilizer according to the claim 8, wherein the lock nut (25) is provided to the lock the coil spring actuator (12) to bottom air bellow mounding brackets (3).