DESC:FIELD OF INVENTION

The present invention relates to rack and pinion steering gear mechanism and particularly to provide an elastomeric member for rack and pinion steering gear mechanism to dampen potential noise. More specifically, the present invention relates to elastomeric member provided on yoke cover, which acts as a cushion, avoiding metal to metal contact and thereby improving the Noise, Vibration and Harshness (NVH) characteristics in an automobile. Further, the present invention aims to improve the performance and durability of rack and pinion steering gear to avoid rattling noise in the field. Also, the elastomeric member of the present invention enhances the performance by ensuring consistency in free pinion torque and due to maintenance of yoke clearance.

DESCRIPTION OF PRIOR ART

Automobiles are equipped with steering mechanism to steer the vehicle in desired direction. In passenger cars, rack and pinion steering mechanism is being used widely. This mechanism converts the rotary motion of the steering wheel into linear movement of the steering linkage and with the help of steering ball joints, it steers the road wheels in the desired direction. During the service life, steering mechanism parts are subjected to wear and tear, thereby resulting in play and vibration while driving over rough roads. The resulting vibration leads to noise and discomfort to the occupants of the automobile.

Referring to Figure 1, a conventional rack and pinion steering gear mechanism consists of rack [11] and pinion [1] which is assembled in to a housing [2]. The pinion [1] is supported by a ball bearing [6] at the top and a needle roller bearing [12] at the bottom. The ball bearing [6] is positively retained with the pinion [1] through a circlip [5]. The pinion bearing sub assembly is retained in place by a pinion cover [4] and an oil seal [3] is provided to prevent dust / dirt entry to the steering gear. The rack [11] is supported by a rack bush at one end and by a support yoke [7] at the other end. The support yoke [7] is provided with a spring [10] and a yoke cover [9] to push the rack [11] against the pinion [1] at all time to have good mesh and positively locked by a lock nut [8]. When the vehicle is run over rough road, the force acted on the rack [11] tends to separate the rack and pinion mesh. The separation fore will be countered by the spring [10] loaded support yoke [7]. More the clearance between the support yoke [7] and yoke cover [9] more the noise it generates since the separation of rack [11] and pinion [1] causes hit noise when it come in contact with each other.

To avoid the rattle noise, normal tendency is to keep a tight yoke clearance which calls for higher accuracy in the rack and pinion gear set. Moreover due to wear and tear, the yoke clearance will increase and result in noise, which will demand frequent adjustment / service in the filed causing inconvenience to the vehicle users.

Some of the prior arts are:
US6119540 discloses a yoke apparatus useful in conjunction with a steering system having a pinion gear and a longitudinally movable rack engaged with the pinion gear. The yoke apparatus comprises a bearing disc received in the aperture, and a pair of biasing members disposed in parallel with one another, each biasing the bearing disc against the rack. One of the biasing members is a compression spring member while the other is an elastomeric O-ring member, or other elastomeric member having a highly non-linear compliance.

DE10349787 discloses a rack-and-pinion steering gear, having a bezel on which slides the rack, and by a closing part inside a seat of the housing of the steering gear is maintained. Between the closure part and the bezel is an elastic element arranged, the bezel keeps in contact with the rack. In addition, an anti-noise element is provided between the bezel and the closure part is arranged, which serves to attenuate the induced in the shoe during use of the motor vehicle axial vibrations.

According, there is a necessity to enhance the performance by providing noise free operation of the steering gear, at the same time ensuring ease of manufacture and without sacrificing product durability.

OBJECTS OF INVENTION
One or more of the problems of the conventional prior art may be overcome by various embodiments of the system and method of the present invention.

Accordingly it is the primary object of the present invention to provide an elastomeric member for rack and pinion steering gear mechanism to dampen potential noise.

It is another object of the present invention to provide an elastomeric member for improving Noise, Vibration and Harshness (NVH) characteristics in rack and pinion steering gear.

Another object of present invention is to improve the performance and durability of rack and pinion steering gear to avoid rattling noise in the field.

It is another object of the present invention to provide an elastomeric member, which eliminates phenomena of spring stiffness drop and provides additional spring effect in the rack and pinion steering gear to retain the rack and pinion mesh.

It is another object of present invention, wherein the elastomeric member is positioned between yoke top face and yoke cover face.

It is another object of the present invention, wherein the elastomeric member enhances the performance by ensuring consistency in free pinion torque and due to maintenance of yoke clearance.

It is another object of the present invention, wherein the elastomeric member with its simple construction aids the manufacturability and product quality (improved performance) of the rack and pinion steering gear.

It is another object of the present invention, wherein the elastomeric member is an O-ring member preferably made up of neoprene material.

SUMMARY OF INVENTION
Thus according to the basic aspect of the present invention there is provided a rack and pinion steering gear mechanism in vehicle comprising: a housing which accommodates at least one rack and one pinion, said pinion is secured in place inside the housing by using a needle bearing at bottom of the housing and a ball bearing at top of the housing which is further secured by a circlip, pinion cover and oil seal; and a yoke assembly fastened into the housing, said yoke assembly comprises of at least one support yoke, spring, yoke cover and lock nut to resist rack and pinion separation characterized in that:
said rack and pinion steering gear mechanism further comprising one or more elastomeric members positioned between the support yoke top face and groove of the yoke cover face to precisely control yoke dampening,
wherein the elastomeric member acts as a cushion, avoiding metal to metal contact, and
wherein the elastomeric member retains required yoke clearance between the pinion and rack during the intended service life of the steering gear.

It is another aspect of the present invention, wherein the elastomeric member is an O-ring member.

It is another aspect of the present invention, wherein the O-ring member provides additional dampening between the support yoke and yoke cover.

It is another aspect of the present invention, wherein the O-ring member provides cushioning between the yoke top face and the yoke cover face of the steering gear providing additional buffer thereby improving Noise, Vibration and Harshness (NVH) characteristics.

It is another aspect of the present invention, wherein the O-ring member eliminates the phenomena of spring stiffness drop and provides additional spring effect to retain the rack and pinion mesh.

It is another aspect of the present invention, wherein the O-ring member provides consistency in free pinion torque.

It is another aspect of the present invention, wherein the O-ring member is preferably made up of neoprene material.

BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1: illustrates the rack and pinion steering gear according to the prior art.
Figure 2: illustrates the rack and pinion steering gear with elastomeric member according to the present invention.
Figure 3: illustrates the exploded/enlarged view of elastomeric member in the rack and pinion steering gear according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention as discussed hereinbefore relates to a rack and pinion steering gear mechanism and particularly to provide an elastomeric member for rack and pinion steering gear mechanism to dampen potential noise.

Referring to Figures 2 and 3, the rack and pinion steering gear mechanism in vehicle comprises of a housing [2] which accommodates at least one rack [11] and one pinion [1], said pinion [1] is secured in place inside the housing [2] by using a needle bearing [12] of the housing [2] and a ball bearing [6] at top of the housing [2] which is further secured by a circlip [5], pinion cover [4] and oil seal [3]; and a yoke assembly is fastened into the housing [2] which comprises of at least one support yoke [7], spring [10], yoke cover [9] and lock nut [8] to resist rack [11] and pinion [1] separation during usage characterized in that said rack and pinion steering gear mechanism of the present invention further comprising of one or more elastomeric members [13] as shown in Figure 3 positioned between the support yoke [7] top face and groove of the yoke cover [9] face to precisely control yoke dampening. The elastomeric member [13] acts as a cushion or provides cushioning effect, avoiding metal to metal contact thereby improving NVH characteristics, performance and durability of an automobile rack and pinion steering gear. Further, the elastomeric member [13] retains the required yoke [7] clearance between pinion [1] and rack [11] during the intended service life of the steering gear. The system is filled with intended lubricant.

The elastomeric member [13] provides additional dampening between support yoke [7] and yoke cover [9], said elastomeric member [13] is an O-ring member [13] made up of neoprene material. The O-ring member [13] provides cushioning between the yoke [7] top face and the yoke cover [9] face of the steering gear providing additional buffer thereby improving NVH characteristics. The O-ring member [13] eliminates the phenomena of spring stiffness drop and provides additional spring effect to retain the rack [11] and pinion [1] mesh and which as observed in prior art is more prone to decay of mechanical properties in spring in the long run or intended service period, said O-ring member [13] enhances the performance by ensuring consistency in free pinion [1] torque and due to maintenance of yoke [7] clearance. The O-ring member [13] with its simple construction aids the manufacturability and product quality such as improved performance of the rack and pinion steering gear.

Thus the O-ring member [13] placed in a groove of the yoke cover [9] according to the present invention improves NVH characteristics, performance and durability of an automobile rack and pinion steering gear. The test results showing the technical effects of the present invention are herewith annexed as Annexure-A-Endurance in positive input test and Annexure B-Bench level noise test report.

,CLAIMS:WE CLAIM:
1. A rack and pinion steering gear mechanism in vehicle comprising: a housing [2] which accommodates at least one rack [11] and one pinion [1], said pinion [1] is secured in place inside the housing [2] by using a needle bearing [12] at bottom of the housing [2] and a ball bearing [6] at top of the housing [2] which is further secured by a circlip [5], pinion cover [4] and oil seal [3]; and a yoke assembly fastened into the housing [2], said yoke assembly comprises of at least one support yoke [7], spring [10], yoke cover [9] and lock nut [8] to resist rack [11] and pinion [1] separation characterized in that:
said rack and pinion steering gear mechanism further comprising one or more elastomeric members [13] positioned between the support yoke [7] top face and groove of the yoke cover [9] face to precisely control yoke dampening,
wherein the elastomeric member [13] acts as a cushion, avoiding metal to metal contact, and
wherein the elastomeric member [13] retains required yoke [7] clearance between the pinion [1] and rack [11] during the intended service life of the steering gear.

2. The rack and pinion steering gear mechanism as claimed in claim 1, wherein the elastomeric member [13] is an O-ring member [13].

3. The rack and pinion steering gear mechanism as claimed in claim 2, wherein the O-ring member [13] provides additional dampening between the support yoke [7] and yoke cover [9].

4. The rack and pinion steering gear mechanism as claimed in claim 3, wherein the O-ring member [13] provides cushioning between the yoke [7] top face and the yoke cover [9] face of the steering gear providing additional buffer thereby improving Noise, Vibration and Harshness (NVH) characteristics.

5. The rack and pinion steering gear mechanism as claimed in claim 4, wherein the O-ring member [13] eliminates the phenomena of spring stiffness drop and provides additional spring effect to retain the rack and pinion mesh.

6. The rack and pinion steering gear mechanism as claimed in claim 5, wherein the O-ring member [13] provides consistency in free pinion [1] torque.

7. The rack and pinion steering gear mechanism as claimed in claim 6, wherein the O-ring member [13] is preferably made up of neoprene material.