A steering column assembly and method of fabricating the same

TECHNICAL FIELD

The subject invention relates to a vehicle steering column, and more particularly to a collapsible steering column.

BACKGROUND OF THE INVENTION

The art is replete with various designs of steering column assemblies, such as, for example, internally collapsing, translating, standard, i.e. non-tilt, and tilt column assemblies. The United States Patent Nos. 5,788,278 to Thomas et al., 6,435,555 to Seamon et al., 6,450,532 to Ryne et al., 6,592,148 to Byers et al., and United States Patent Application Publication No. 2002/0121771 to Shifflett et al. disclose different designs of the steering column assemblies. The stiffness characteristics of the steering column assembly designs depend on common mathematical models and engineering software (FEA), which do not provide accurate determination of the stiffness. The inaccuracy in determination of the stiffness of the steering column assembly results in design changes after experimental testing.

There is a constant need in area of steering column assembly designs for an assembly wherein the stiffness of the jacket is determined before installation of the assembly on the vehicle and experimental testing and for the assembly having improved packaging characteristics to hold various components of the assembly such as wires, ECL mechanisms, steering tube position sensors, BSTI switches, and the like.

BRIEF SUMMARY OF INVENTION

A steering column assembly of the present invention includes a lower support bracket and an upper support bracket. The steering column assembly includes a yoke support housing and a plurality of tubes spaced from one another circumferentially about a longitudinal axis and rigidly interconnecting the yoke support housing and the upper support bracket. A jacket is fixed to one of the lower and upper support brackets and is slidable relative to the other of the lower and upper support brackets about the longitudinal axis between an uncollapsed position and a collapsed position of said steering column assembly.

The present invention includes a method of fabricating the steering column assembly having the lower support bracket and the upper support bracket presenting a longitudinal axis disposed within and extending through the lower support bracket and the upper support bracket. The method includes the steps of positioning the yoke support housing adjacent to the upper support bracket, selecting a group of tubes from a plurality of tube configurations, and mechanically interconnecting the yoke support housing with the upper support bracket by disposing the group of tubes therebetween and by spacing the tubes from one another circumferentially about the longitudinal axis. The method includes the step of disposing the jacket fixed to one of the lower and upper support bracket to facilitate slidably movement of the jacket relative to the other of the lower and the upper support brackets about the longitudinal axis between an uncollapsed position and a collapsed position of the steering column assembly.

An advantage of the present invention is to provide the steering column assembly design that achieves a high section modulus, and improved and predetermined stiffness characteristics.

Another advantage of the present design is to provide the steering column assembly having improved packaging characteristics to hold various components of a tilt assembly.

Still another advantage of the present invention is to provide the steering column assembly having the yoke support housing interconnected with the upper support bracket and the jacket fixed between the upper and lower support brackets. This design facilitates easier and more reliable movement of the jacket relative to one of the lower and the upper support brackets about the longitudinal axis between the uncollapsed and collapsed position of the steering column assembly thereby eliminating need to translate tubes of prior art design through the corresponding holes defined in the prior art upper and lower brackets for spanning the entire prior art steering column.

Still another advantage of the present invention is to provide tubes interconnecting the upper support bracket and the yoke support housing to store wires and other devices within the tubes, thereby providing the tubes with wire routing and wire protecting features at no additional cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: <ul id="ul0001" list-style="none" compact="compact"><li>Figure 1 is an exploded perspective view of a steering column assembly having upper and lower support brackets interconnected by a jacket disposed therein, and a yoke support housing interconnected with the upper support bracket by a plurality of tubes;</li><li>Figure 2 is another perspective view of the steering column assembly, partially cut away and in cross section</li><li>Figure 3 is a cross sectional view of one of the tubes;</li><li>Figure 4 is a cross sectional view of an alternative embodiment of the tube;</li><li>Figure 5 is a cross sectional view of still another alternative embodiment of the tube;</li><li>Figures 6 is a plan view of the steering column assembly;</li><li>Figure 7 is a plan view of the steering column assembly, wherein the upper support bracket, connected with the yoke support housing, is moved axially along the jacket to the lower support bracket during a collision;</li><li>Figure 8 is a plan view of the steering column assembly, wherein the jacket connected to the upper support bracket, is moved axially through the lower support bracket during the collision;</li><li>Figure 9 is a graph showing impact of the tube length on a deflection of the tube with respect to a longitudinal axis of the steering column assembly, and</li><li>Figure 10 shows steps of a method of fabricating the steering column assembly.</li></ul>

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures wherein like numerals indicate like or corresponding parts throughout the several views, a steering column assembly of the present invention is generally shown at <b>100.</b>

The steering column assembly <b>100</b> of the present invention includes a lower support bracket <b>102,</b> an upper support bracket <b>104,</b> and a jacket <b>106</b> disposed within and extending along a longitudinal axis <b>O</b> through the lower support bracket <b>102</b> and the upper support bracket <b>104.</b> The steering column assembly <b>100</b> includes a yoke support housing <b>108</b> and a plurality of tubes <b>110</b> spaced from one another circumferentially about the longitudinal axis <b>O</b> of the jacket <b>106</b> and interconnecting the yoke support housing <b>108</b> and the upper support bracket <b>104.</b>

Referring to Figures 1 and 2, the lower support bracket <b>102</b> of the present invention includes a generally rectangular configuration and is designed for connecting the steering column assembly <b>100</b> to a body of a vehicle (not shown). The lower support bracket <b>102</b> has top <b>111,</b> bottom <b>112,</b> side walls <b>114, 116,</b> and front <b>118</b> and rear <b>120</b> ends. The lower support bracket <b>102</b> includes an opening <b>122</b> defined therewithin. The lower support bracket <b>102</b> is preferably injection molded from a plastic or polymer material, however it should be recognized that it can also be molded or machined from a metallic material such as steel or aluminum.

The upper support bracket <b>104</b> has a generally rectangular configuration and is designed for connecting the steering column assembly <b>100</b> to the body of the vehicle adjacent from the point of connection of the lower support bracket <b>102.</b> The upper support bracket <b>104</b> includes top side <b>124,</b> bottom side <b>126,</b> side walls <b>128, 130</b> interconnected therebetween at the respective tops to define a peripheral edge, generally indicated at <b>132.</b> The upper support bracket <b>104</b> further includes rear <b>134</b> and front <b>136</b> ends and a boss section <b>138</b> integral with the upper support bracket <b>104</b> and extending from the rear end <b>134</b> to the front end <b>136.</b> The boss section <b>138</b> includes an inlet of a generally circular configuration, generally indicated at <b>140,</b> defined therewithin to receive the jacket <b>106</b> stationary engaged within the inlet <b>140.</b>

Referring back to Figure 1, the upper support bracket <b>104</b> includes interior pockets <b>142</b> spaced one from the other and defined around the peripheral edge <b>132</b> at the front end <b>136</b> of the upper support bracket <b>104.</b> The interior pockets <b>142</b> are interconnected with the boss section <b>138</b> by a wall <b>144,</b> respectively, to increase stiffness of the upper support bracket <b>104.</b> The upper support bracket <b>104</b> includes a flange <b>146</b> integral with and extending outwardly from each of the side walls <b>128, 130</b> in a cantelivered fashion. Each flange <b>146</b> includes a slot <b>148</b> defined therewithin to receive a shear device (not shown) activated during a collision of a vehicle. The upper support bracket <b>104</b> is preferably injection molded from a plastic or polymer material, however it should be recognized that it can also be molded or machined from a metallic material such as steel or aluminum.

The jacket <b>106</b> of the steering column assembly <b>100</b> includes a generally tubular configuration and has the terminal ends <b>150, 152.</b> The jacket <b>106</b> includes a first sleeve <b>154,</b> as best shown in Figure 1, disposed annularly about one of the terminal ends <b>150</b> of the jacket <b>106</b> and between the lower support bracket <b>102.</b> The first sleeve <b>154</b> prevents frictional engagement between the jacket <b>106</b> sliding through the lower support bracket <b>102</b> in case of a collision.

The jacket <b>106</b> includes a second sleeve (not shown), similar disposed annularly about another telescoping end <b>152</b> of the jacket <b>106</b> and between the upper support bracket <b>104.</b> The second sleeve prevents frictional engagement between the jacket <b>106</b> sliding through the upper support bracket <b>104</b> in case of the collision. The lower support bracket <b>102</b> and the upper support bracket <b>104</b> are stationary mounted to the body of the vehicle. During the collision, the upper <b>104</b> and lower <b>102</b> support brackets collapse internally with respect to one another. Figure 7, for example, shows the steering column assembly <b>100</b> in an internally collapsing mode, wherein the jacket <b>106</b> is connected to the lower support bracket <b>102</b> and extends through and beyond the upper support bracket <b>104</b> still maintaining stiffness between the upper support bracket <b>104</b> and the yoke support housing <b>108.</b> Alternatively, as shown in Figure 8, the steering column assembly <b>100</b> is shown in a translating mode, wherein the jacket <b>106</b> is connected to the upper support bracket <b>104</b> and extends through and beyond the lower support bracket <b>102</b> still maintaining stiffness between the upper support bracket <b>104</b> and the yoke support housing <b>108.</b> The jacket <b>106</b> and the sleeves <b>156</b> are preferably injection molded from a plastic or polymer material, however it should be recognized that it can also be molded or machined from a metallic material such as steel or aluminum.

As best shown in Figure 1, the yoke support housing <b>108</b> is designed to mechanically engage a tilt assembly <b>158</b> therewithin. The yoke support housing <b>108</b> includes a generally rectangular configuration and has rear <b>160</b> and front <b>162</b> ends, top <b>164,</b> bottom <b>166,</b> and sides <b>168, 170</b> interconnected one with the other. The yoke support housing <b>108</b> includes a hole of a circular configuration, generally indicated at <b>172,</b> defined therewithin and spaced longitudinally and axially with respect to the jacket <b>106.</b> The yoke support housing <b>108</b> includes a projection <b>174</b> integral with and extending outwardly from each of the sides <b>168, 170</b> at the front end <b>162</b> of the yoke support housing <b>108</b> to engage the tilt assembly <b>158.</b> The yoke support housing <b>108</b> includes exterior pockets <b>180</b> integral with the yoke support housing <b>108</b> at the top <b>164,</b> bottom <b>166</b> and sides <b>168, 170.</b> The exterior pockets <b>180</b> are spaced longitudinally and adjacent the interior pockets <b>142</b> of the upper support bracket <b>104.</b>

Referring to Figures 1 through 3, the invention includes four tubes <b>110</b> having a body defining inner <b>182</b> and outer <b>184</b> diameters, as view in cross section, and terminal ends <b>186, 188,</b> respectively. The tubes <b>110</b> are spaced from one another circumferentially about the longitudinal axis <b>O</b> of the jacket <b>106</b> and interconnecting the yoke support housing <b>108</b> and the upper support bracket <b>104.</b> The tubes <b>110</b> are mechanically connected with the internal pockets <b>142</b> of the upper support bracket <b>104</b> and exterior pockets <b>180</b> of the yoke support housing <b>108.</b> The tubes <b>110</b> include an equal and predetermined thickness between the outer <b>184</b> and inner <b>182</b> diameters, wherein the outer diameter <b>184</b> is complimentary to predetermined inner diameter <b>143</b> of the interior pockets <b>142</b> and inner diameter <b>181</b> of the exterior pockets <b>180.</b> In an alternative embodiment of the present invention, as shown in Figures 4 and 5, the tubes <b>110</b> may include triangular and rectangular configurations, as viewed in cross section. The interior pockets <b>142</b> of the upper support bracket <b>104</b> and the exterior pockets <b>180</b> of the yoke support housing <b>108</b> of the alternative embodiment include triangular and rectangular configurations, (not shown) to mate with the respective tubes <b>110</b> defining triangular <b>185,</b> rectangular <b>187</b> configurations, respectively, as shown in Figures 4 and 5. The outer diameter <b>184</b> of the tube <b>110</b> is constant wherein the inner diameter <b>182</b> has a variable value with respect to different designs of the steering column assembly <b>100</b> to increase stiffness of the assembly <b>100</b> thereby increasing moment of Inertia. The steering column assembly <b>100</b> includes a shaft <b>189</b> extending through the yoke support housing <b>108,</b> the jacket <b>106,</b> the upper <b>104</b> and lower <b>102</b> support brackets of the steering column assembly <b>100.</b>

As it appears from the results of a calculation based on a formula provided further below, the increased distance between the outer <b>184</b> and inner <b>182</b> diameters of the tubes <b>110,</b> (i.e., wall thickness) provides for better stiffness of the assembly <b>100.</b> An impact of the tube thickness to the moment of Inertia is shown in the formula:<maths id="math0001" num=""><img file="EP1568567A1_D0001.tif" /></maths><maths id="math0002" num=""><img file="EP1568567A1_D0002.tif" /></maths>    where, <i>Ix</i> is a moment of Inertia distributed along axis <i>x</i>, extending horizontally from the longitudinal axis,    <i>Iy</i> is a moment of Inertia distributed along axis <i>y</i>, extending vertically from the longitudinal axis <b>O,</b>    <i>Do</i> is the outer diameter <b>184</b> of the tube <b>110,</b>    <i>Di</i> is the inner diameter <b>182</b> of the tube <b>110,</b>    <i>dx</i> is a distance from the longitudinal axis <b>O</b> in the axis <i>x</i> direction,    <i>dy</i> is a distance from the longitudinal axis <b>O</b> in the axis <i>y</i> direction, and    π is a ration of a circumference of the tube <b>110</b> as view in cross section, divided into a diameter of the tube <b>110,</b> wherein π has a constant value of 3.14.

For example, in a first test, wherein the value of the outer diameter <b>184</b> is .0127 and the value of the inner diameter <b>182</b> is .0117 with a wall thickness of .001 defined therebetween, as view in cross section, and the distance from the longitudinal axis <b>O</b> in the axis <i>x</i> and <i>y</i> directions is .034 - the moment of Inertia distributed along said axis <i>x</i> and <i>y</i> is 9.004E-8. In a second test, wherein the value of the outer diameter <b>184</b> remains the same and the value of the inner diameter <b>182</b> is diminished from .0117 to .0037 to receive a wall thickness of .009 defined therebetween, as view in cross section, and, as shown in the first test, the distance from the longitudinal axis <b>O</b> in the axis <i>x</i> and <i>y</i> directions remains .034 - the moment of Inertia distributed along the axis <i>x</i> and <i>y</i> is 5.411 E-7. The results of these tests show that as the wall thickness between the inner <b>182</b> and outer diameter <b>184</b> of the tube <b>110</b> is increased, the moment of Inertia is increased that results in the increased stiffness of the steering column assembly <b>100.</b>

In addition, an impact of the tube <b>110</b> separation is proved by using the aforementioned formula, wherein in the first and second tests the value of the outer diameter <b>184</b> of the tube <b>110</b> is .0127 and the value of the inner diameter <b>182</b> is .0117 with a thickness of .001 defined therebetween, as view in cross section. The distance from the longitudinal axis <b>O</b> in the axis <i>x</i> and <i>y</i> directions varies from .034 to .054, respectively. The results of these tests show that as the distance from the longitudinal axis <b>O</b> is increased from .034 to .054, the moment of Inertia is increased from 9.004E-8 to 2.25E-7, which results in the increased stiffness of the steering column assembly <b>100.</b>

In addition to the tube separation and tube wall thickness, the length of the tube <b>110</b> with respect to each individual design of the steering column assembly <b>100</b> provides for increased stiffness of the steering column assembly <b>100,</b> as shown in Figure 9. For example, an impact of the tube <b>110</b> length to a deflection <i>V</i> is shown in the formula:<maths id="math0003" num=""><math display="block"><mrow><mfrac><mrow><mtext mathvariant="italic">P</mtext><mtext>(</mtext><mtext mathvariant="italic">b</mtext><mtext> + </mtext><mtext mathvariant="italic">x</mtext><msup><mrow><mtext>)</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><mtext> (</mtext><mtext mathvariant="italic">a</mtext><mtext> + </mtext><mtext mathvariant="italic">b</mtext><mtext> + </mtext><mtext mathvariant="italic">x</mtext><mtext>)</mtext></mrow><mrow><mtext>3</mtext><mtext mathvariant="italic">EI</mtext></mrow></mfrac><mtext> 〉 </mtext><mfrac><mrow><msup><mrow><mtext mathvariant="italic">Pb</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><mtext></mtext><mtext mathvariant="italic">L</mtext></mrow><mrow><mtext>3</mtext><mtext mathvariant="italic">EI</mtext></mrow></mfrac><mtext> 〉 </mtext><mfrac><mrow><mtext mathvariant="italic">P</mtext><mtext>(</mtext><mtext mathvariant="italic">b</mtext><mtext> - </mtext><mtext mathvariant="italic">x</mtext><msup><mrow><mtext>)</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><mtext> (</mtext><mtext mathvariant="italic">a</mtext><mtext> + </mtext><mtext mathvariant="italic">b</mtext><mtext> - </mtext><mtext mathvariant="italic">x</mtext><mtext>)</mtext></mrow><mrow><mtext>3</mtext><mtext mathvariant="italic">EI</mtext></mrow></mfrac></mrow></math><img file="EP1568567A1_D0003.tif" /></maths>    where, <i>I</i> is a moment of Inertia,    <i>P</i> is a mass of a load provided by the yoke support housing <b>108,</b>    <i>L</i> is the length of the tube <b>110,</b>    <i>E</i> is a modulus of elasticity of the tube <b>110,</b>    <i>a</i> is a distance between the lower support bracket <b>102</b> and the upper support bracket <b>104</b> connected to the body of the vehicle,    <i>b</i> is a distance between the upper support bracket <b>104</b> and the yoke support housing <b>108,</b> and    <i>x</i> is a value of a increased distance of <i>b</i>. This formula shows that the increased distance of <i>b</i> increases the deflection from <i>V1</i> to <i>V2</i> between the longitudinal axis <b>O</b> and the yoke support housing <b>108,</b> thereby decreasing the stiffness and the moment of Inertia of the steering column assembly <b>100.</b>

The design of the present invention achieves a high section modulus, which has a proportional influence to the natural frequency of the steering column assembly <b>100</b> through the stiffness. The advantages of the present design include improved packaging characteristics, unlike typical column assembly designs, shown in aforementioned United States Patent No. 6,592,148 to Byers et al. and United States Patent Application Publication No. 2002/0121771 to Shifflett et al. A space defined between the upper support bracket <b>104</b> and the yoke support housing <b>108</b> interconnected and spaced apart by the tubes <b>110,</b> define a gap, generally indicated at <b>190,</b> to hold various components of the tilt assembly <b>158</b> including ECL mechanisms, steering tube position sensors, BSTI switches, and the like (not shown). In addition, the tubular geometry of the tubes <b>110</b> provides for ability to store wires <b>192</b> and other devices within the tubes <b>110,</b> thereby providing the tubes <b>110</b> with wire routing and wire protecting features at no additional cost.

The invention includes a method, generally indicated at <b>200,</b> of fabricating the steering column assembly <b>100,</b> as shown in Figure 10. The method <b>200</b> begins with positioning <b>202</b> the yoke support housing <b>108</b> adjacent the upper support bracket <b>104.</b> The next step (not shown) includes selecting the group of tubes <b>110</b> having the inner <b>182</b> and outer <b>184</b> diameters from a plurality of tube configurations. The next step of the method <b>200</b> includes connecting <b>204</b> the yoke support housing <b>108</b> to the upper support bracket <b>104,</b> wherein the yoke support housing <b>108</b> is longitudinally spaced from the upper support bracket <b>104</b> by the group of four tubes <b>110</b> equally spaced from one another. The step of connecting <b>204</b> the yoke support housing <b>108</b> to the upper support bracket <b>104</b> further includes disposing the tubes <b>110</b> having an equal and predetermined thickness between the outer <b>184</b> and inner <b>182</b> diameters, as viewed in cross section. The tubes <b>110</b> are mechanically interconnected within the interior pockets <b>142</b> of the upper support bracket <b>104</b> at one of the terminal ends <b>186</b> and within the exterior pockets <b>180</b> of the yoke support housing <b>108</b> at another terminal end <b>188,</b> respectively. As appreciated by those skilled in the art, various methods of interconnecting the tubes <b>110</b> within the upper support bracket <b>104</b> and the yoke support housing <b>108</b> are provided. Preferably, the tubes <b>110</b> are being press stamped within the upper support bracket <b>104</b> and the yoke support housing <b>108.</b> Alternatively, the tubes <b>110</b> may include male connectors (not shown) to complement with female connectors (not shown) defined within the interior pockets <b>142</b> of the upper support bracket <b>104</b> and exterior pockets <b>180</b> of the yoke support housing <b>108.</b> The step of connecting <b>204</b> the yoke support housing <b>108</b> to the upper support bracket <b>104</b> of the method <b>200</b> further includes the step of disposing <b>206</b> a jacket <b>106</b> fixed to one of the lower <b>102</b> and upper <b>104</b> support bracket to facilitate slidably movement of the jacket <b>106</b> relative to the other of the lower <b>102</b> and the upper <b>104</b> support brackets about the longitudinal axis <b>O</b> between an uncollapsed position and a collapsed position of the steering column assembly <b>100.</b>

With respect to different embodiments of the steering column assembly <b>100,</b> the jacket <b>106</b> requires the sleeve <b>154</b> to prevent frictional engagement between the jacket <b>106</b> and the upper and lower <b>102</b> support brackets. In another alternative embodiment, the method <b>200</b> includes the step of disposing (not shown) the sleeve <b>154</b> annularly about another terminal <b>152</b> end of the jacket <b>106</b> and between the upper support bracket <b>104.</b> In one alternative embodiment, the method <b>200</b> includes the step of disposing the sleeve <b>154</b> annularly about one of the terminal ends <b>150</b> of the jacket <b>106</b> and between the lower support bracket <b>102</b> (not shown).

While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.