Claims:1. A steering column assembly (100), comprising:
a top steering shaft (102), wherein the top steering shaft (102) is connected to a first piston (104) at one end and a steering wheel (106) at other end, wherein the first piston (104) comprises a set of valves (108) installed on the surface of the first piston (104); and
a damper tube (110) connecting the top steering shaft (102) with a bottom steering shaft (122), wherein the damper tube (110) comprises:
a second piston (112) configured to partition the damper tube (110) into a gas chamber (114) and an oil chamber (116), wherein the oil chamber (116) being configured to accommodate the first piston (104), wherein the first piston (104) divides the oil chamber (116) into a top oil compartment (116a) and a bottom oil compartment (116b), and
wherein during vehicle crash, generated impact force on the steering wheel (106) gets transferred to the top steering shaft (108) and after pre-defined collapse load on the first piston (104), the valves (108) opens and the first piston (104) starts moving down under the hydraulic pressure by moving the second piston (112) and thereby compressing the gas in the gas chamber (114), and, wherein the second piston (112) and the top steering shaft (102) gets back to original position when compressed gas decompresses to its original position.

2. The steering column assembly (100) of claim 1, further comprises:
an outer tube (118) encapsulating the damper tube (110);
a set of needle bearings (120) mounted on the inner surface of the outer tube (118), wherein the set of needle bearings (120) is configured to support the damper tune (110) and transfer turning torque to the bottom steering shaft (122).

3. The steering column assembly (100) of claim 1, wherein during the frontal crash, hydraulic liquid from the bottom oil compartment (116b) is steadily transfer to the top oil compartment (116a) through the set of valves (108) and gas from the gas chamber (114) is compressed for absorbing the impact force generated during the frontal crash, and wherein the top steering shaft (102) is shifted from the original position to the compressed position.

4. The steering column assembly of claim 3, wherein after the frontal crash the hydraulic liquid from the top oil compartment (116a) is steadily transfer to the bottom oil compartment (116b) and gas from the gas chamber (114) is decompressed, and wherein after the frontal crash, the top steering shaft (102) is shifted from the compressed position to the original position gradually.

5. The steering column assembly of claim 1, wherein the first piston (104) is enabled with a piston lock (202), wherein the piston lock (202) prevents axial movement of the first piston (104) during normal operation of the vehicle.

6. The steering column assembly of claim 5, wherein the piston lock (202) is configured to break when the impact force is more than a predefined threshold value, and wherein the first piston (104) is free to move axially after the piston lock (202) is broken.

7. The steering column assembly of claim 1, wherein the set of valves (108) connect the top oil compartment (116a) with a bottom oil compartment (116b) for transfer of hydraulic fluid during frontal crash and after frontal crash.

8. The steering column assembly of claim 1, wherein the set of valves (108) comprise one or more compression valves and one or more decompression valves, wherein the one or more compression valves are configured to open during a frontal crash, and wherein the one or more decompression valves are configured to open after the frontal crash.

9. The steering column assembly of claim 5, wherein the piston lock (202) is enabled on the periphery of the first piston (104) for restricting the rotary motion of the top steering shaft (102) and first piston (104).

10. The steering column assembly of claim 1, the bottom steering shaft (122) is further connected to an I-shaft, wherein the I-shaft is configured to transfer turning torque from the steering wheel to a rack and pinion assembly for operation road wheels of the vehicle.
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
A STEERING COLUMN ASSEMBLY

Applicant:
Tata Motors Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400001, Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.
TECHNICAL FIELD
[001] The present subject matter described herein, in general, relates to a steering column and more particularly a steering column collapse feature for absorbing frontal crash impact.

BACKGROUND
[002] The primary functions of a steering column in a vehicle is to connect the steering wheel to the steering mechanism and transfer driver’s input torque from the steering wheel to road wheels. Apart from transferring the input torque to the road wheels, energy absorption in event of the vehicle frontal crash is one of the key auxiliary features of the steering column.
[003] For the purpose of energy absorption in event of the vehicle frontal crash, at present, steering column with the ball slider collapsible feature is widely used in almost all the automotive passenger vehicles. During the vehicle frontal crash, steering column collapses after the certain impact on steering wheel (approx. 4-5KN) by shearing collapse capsules and the steering column moves down through the ball slider sleeve for a predefined collapse stroke (approx. 60-80 mm) which absorb the impact energy and that help to minimize the injury to a driver.
[004] However, due to the ball slider collapse mechanism in present steering column, there is a permanent deformation in the steering column assembly. After the frontal crash, the steering column assembly is rendered useless and needs to be completely replaced in service repair.

SUMMARY
[005] Before the present steering column assembly 100, is described, it is to be understood that this application is not limited to the particular assembly described, as there can be multiple possible embodiments which are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular implementations or versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to steering column assembly 100. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
[006] In one implementation, a steering column assembly 100 is illustrated. The steering column assembly 100 comprises a top steering shaft 102. The top steering shaft 102 is connected to a first piston 104 at one end and a steering wheel 106 at other end. In one embodiment the first piston 104 comprises a set of valves 108 installed on the surface of the first piston 104. Further, the steering column assembly 100 comprises a damper tube 110 connecting the top steering shaft 102 with a bottom steering shaft 122. The damper tube 110 comprises a second piston 112 configured to partition the damper tube 110 into a gas chamber 114 and an oil chamber 116. In one embodiment, the oil chamber 116 is configured to accommodate the first piston 104, wherein the first piston 104 divides the oil chamber 116 into a top oil compartment 116a and a bottom oil compartment 116b. Further, during vehicle crash, generated impact force on a steering wheel 106 gets transferred to the top steering shaft (108) and after pre-defined collapse load on the first piston 104, the set of valves 108 opens and the first piston 104 starts moving down under the hydraulic pressure by moving the second piston 112 and thereby compressing the gas in the gas chamber 114. Furthermore, the first piston 104 and the top steering shaft 102 gets back to original position gradually when compressed gas decompresses to its original position.

BRIEF DESCRIPTION OF THE DRAWINGS
[007] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating of the present subject matter, an example of construction of the present subject matter is provided as figures; however, the invention is not limited to the specific method and assembly disclosed in the document and the figures.
[008] The present subject matter is described detail with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer various features of the present subject matter.
[009] Fig 1 illustrates a steering column assembly 100, in accordance with an embodiment of the present subject matter.
[010] Fig 2(a) illustrates sectional view of a first piston 104 of the steering column assembly 100, in accordance with an embodiment of the present subject matter.
[011] Fig 2(b) illustrates a compression valve and decompression valve of the first piston 104 in accordance with an embodiment of the present subject matter.
[012] Fig 3 illustrates the different operation modes associated with the steering column assembly 100 during and after collapse in a frontal crash in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION
[013] In an implementation, a steering column assembly of a vehicle is illustrated. The steering column assembly comprises a damper tube coaxially connecting a top steering shaft with a bottom steering shaft. The damper tube is configured to house a first piston and a second piston. The second piston partitions the damper tube into a gas chamber and an oil chamber. Further, the top steering shaft is integrated with the first piston. The first piston comprises a set of valves, wherein the first piston is placed inside the oil chamber of the damper tube and partitions the oil chamber into a top oil compartment and a bottom oil compartment. Further, the damper tube is encapsulated inside an outer tube. In one embodiment, the damper tube is supported by needle roller bearings placed under the outer tube. The needle roller bearings enable transfer of the rotary motion from the steering wheel to the bottom steering shaft and thereafter to an I-shaft (through UJ1) after the driver applies torque at steering wheel connected to the top steering shaft. The I-shaft is configured to transfer turning torque from the steering wheel to a rack and pinion assembly for operation road wheels of the vehicle.
[014] In one embodiment, during vehicle frontal crash, the crash impact force generated on the steering wheel are transferred to top steering shaft and the set of valves. In one embodiment, after a pre-defined collapse load (4-5KN load) on the first piston, the set of valves open and the first piston along with the top steering shaft start moving down under the influence of hydraulic pressure. Furthermore, the first piston stops at pre-defined collapse stroke (approx. 60-80mm) after absorbing the crash impact energy. In one embodiment, piston locks are enabled over the first piston in order to restrict the rotary motion of the top steering shaft and first piston inside the damper tube. Further, the piston locks guide the top steering shaft and first piston inside the damper tube in axial direction only.
[015] In one embodiment, during the collapse, the hydraulic fluid in the oil chamber and high pressure gas in the gas chamber absorb impact energy and helps in minimizing injury to a driver of the vehicle. Since the damper tube works on the principle of hydraulic/gas filled damper, first piston and top steering shaft resume slowly back to its original position when compressed gas is decompressed after a frontal crash event.
[016] In one embodiment, the steering column assembly is configured to operate in three different phases:
[017] I. Before Frontal Crash State: the top steering shaft is at original position without any axial movement.
[018] II. During Frontal Crash State: the top steering shaft along with first piston moved down to a compressed position.
[019] III. After Frontal Crash State: the top steering shaft along with first piston moved up to the original position from the compressed position gradually.
[020] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any assembly and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, assembly and methods are now described. The disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments described, but is to be accorded the widest scope consistent with the principles and features described herein.
[021] Referring now to Fig 1, a steering column assembly 100 of a vehicle, is illustrated. The steering column assembly 100 comprises a top steering shaft 102. The top steering shaft 102 is connected to a first piston 104 (hydraulic piston) at one end and a steering wheel 106 at other end.
[022] Further, the steering column assembly 100 comprises a damper tube 110 placed between the top steering shaft 102 with a bottom steering shaft 122. The damper tube 110 comprises a second piston 112 (free piston) configured to partition the damper tube 110 into a gas chamber 114 and an oil chamber 116. The movement of the second piston 112 may be axially restricted by one or more guide channels. The one or more guide channels may be enabled on the inner surface of the damper tube 110. The gas chamber 114 may be configured to accommodate high-pressured gas. The gas from the gas chamber 114 may be selected from a group of air, Nitrogen, or inert gases. Further, the oil chamber 116 may be configured to maintain hydraulic fluid. The hydraulic fluid may be selected from a group of mineral oil, water, phosphate ester, water-based ethylene glycol compounds, and silicone fluids. In one embodiment, the oil chamber 116 is configured to accommodate the first piston 104. In one embodiment, the first piston 104 divides the oil chamber 116 into a top oil compartment 116a and a bottom oil compartment 116b. Furthermore, the first piston 104 may comprises a set of valves 108 installed on the surface of the first piston 104. The set of valves 108 may comprise one or more compression valves and one or more decompression valves.
[023] Further, during vehicle crash, the generated impact force on the steering wheel 106 gets transferred to the top steering shaft 108 and after pre-defined collapse load on the first piston 104, the set of valves 108 opens and the first piston 104 starts moving down under the hydraulic pressure by moving the second piston 112 and thereby compressing the gas in the gas chamber 114. Further, the first piston 104 and the top steering shaft 102 gets back to original position slowly when compressed gas decompresses to its original position. Furthermore, a set of needle bearings 120 are placed between the outer tube 118 and the damper tube 110. The set of needle bearings 120 transferring the rotary motion of the top steering shaft 102 to the bottom steering shaft 120 and thereafter to an I-shaft (through UJ1) after the driver applies torque at steering wheel 106 connected to the top steering shaft 102. The working of the first piston 104 is further explained with reference to figure 2a and figure 2b.
[024] Figure 2a illustrates sectional view of the first piston 104 and the set of valves 108, in accordance with an embodiment of the present subject matter. The set of valves 108 connect the top oil compartment 116a with a bottom oil compartment 116b for transfer of hydraulic fluid during frontal crash and after frontal crash. The first piston 104 further comprises one or more piston locks 202. In one embodiment, the piston locks 202 are enabled on the periphery of the first piston 104 in order to restrict the rotary motion of the top steering shaft 102 and first piston 104. Further, the piston locks 202 guide the top steering shaft 102 and first piston 104 inside the damper tube 110 in axial direction only. Furthermore, the piston lock 202 prevents axial movement of the first piston 104 during normal operation of the vehicle. In one embodiment, the piston lock 202 is configured to break when the impact force of the frontal crash is more than a predefined threshold value. Once the piston lock 202 breaks, the first piston 104 is free to move axially along the steering assembly 100.
[025] Figure 2b illustrate operation of the set of valves 108 of the first piston 104 in accordance with an embodiment of the present subject matter. In one embodiment, the set of valves 108 may comprise one or more compression valves and one or more decompression valves. The one or more compression valves may be configured to open during a frontal crash, and wherein the one or more decompression valves are configured to open after the frontal crash. In one embodiment, the set of valves 108 may comprise at least one compression valve 204 and at least one decompression valve 206. The compression valve 204 is in open state during frontal crash of the vehicle, whereas the decompression valve 206 is in open state after frontal crash of the vehicle.
[026] In one embodiment, the compression valve 204 may comprise of a compression channel 204a and a compression plate 204b. The compression channel 204a connects the bottom oil compartment 116b with the top oil compartment 116a. Furthermore, the compression plate 204b is placed in the top oil compartment 116a and operates only during frontal crash such that the fluid from the bottom oil compartment 116b flows through the compression valve 204 and enters the top oil compartment 116a.
[027] In one embodiment, the decompression valve 206 may comprise of a decompression channel 206a and a decompression plate 206b. The decompression channel 206a connects the top oil compartment 116a with the bottom oil compartment 116b. Furthermore, the decompression plate 206a is placed in bottom oil compartment 116b and operates only after the frontal crash such that the fluid from the top oil compartment 116a flows through the compression valve 206 and enters the bottom oil compartment 116b. The operation of the damper tube 110 before frontal crash, during frontal crash and after frontal crash 306 is disclosed in detail with reference to figure 3.
[028] Referring now to figure 3, the different operation modes associated with the steering column assembly 100 during and after collapse in a frontal crash are illustrated in accordance with an embodiment of the present subject matter. The damper tube 110 enables steering column assembly 100 to operate in three different modes namely a Before Frontal Crash 302, a During Frontal Crash 304 and a After Frontal Crash 306.
[029] In one embodiment, Before Frontal Crash 302, the valves 204 and 206 are in closed state of operation and the torque applied to steering wheel 106 is transferred to the turning road wheels. The pressure of the gas in the gas chamber 114 and pressure of the hydraulic fluid in the oil chamber 116 is at equilibrium. Due to this, the second piston 112 is maintained at a fixed location. Furthermore, since the set of valves 108 is configured to operate at 4 – 5 K Newton force, bidirectional flow of the hydraulic fluids between the top oil compartment 116a and the bottom oil compartment 116b is prevented. Thus, the first piston 104 and the top steering shaft are maintained at a static/ original position. Furthermore, before frontal crash 302, the set of needle bearings 120 is configured to support the damper tune 110 and transfer turning torque applied by the driver on the steering wheel to the bottom steering shaft 122 for controlling the direction of the vehicle.
[030] In one embodiment, During Frontal Crash 304 of the vehicle, the set of valves 108 is actuated for absorbing the impact force generated during the frontal crash. Furthermore, During Frontal Crash 304, the steering wheel 106 and the top steering shaft 102 exert impact forces on the first piston 104. As a result, the hydraulic liquid from the bottom oil compartment 116b is steadily transfer to the top oil compartment 116a and gas from the gas chamber (114) is compressed due to the instantaneous impact forces. Due to the compression of the gas from the gas chamber and transfer of hydraulic fluid from the bottom oil compartment 116b to the top oil compartment 116a, the top steering shaft 102 is shifted from the original position to the compressed position. Due to the shift in the top steering shaft 102 under the influence of impact forces, a considerable amount of impact energy is absorbed in collapse stroke.
[031] In one embodiment, After Frontal Crash 306 of the vehicle, compressed gas from the gas chamber 114 exerts force on the second piston 112. As a result, the second piston 112 moves towards the top steering shaft 102 and exerts force on the bottom oil compartment 116b. The hydraulic fluid from the bottom oil compartment 116b intern exerts forces on the first piston 104. As a result, the set of valves 108 are actuated and the hydraulic fluid from the top oil compartment 116a flows to the bottom oil compartment 116b. Due to this transfer of hydraulic fluid, the top steering shaft 102 is shifted from the compressed position back to the original position gradually.
[032] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[033] Some embodiments of the steering column assembly 100 enables reduction in injury index compare to the ball slider collapsible column designs available in the art because of the hydraulic dampening effect.
[034] Some embodiments of the steering column assembly 100 enables reduction in road shocks/vibration at steering wheel.
[035] Some embodiments of the steering column assembly 100 enables simple construction of steering column without the use crushing tube.
[036] Some embodiments of the steering column assembly 100 enables reduction in service cost since there is no need to replace entire steering column assembly after the vehicle crash.
[037] Although implementations of steering column assembly have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features are disclosed as examples of steering column assembly.