阅读说明：本技术 转向柱组件 (Steering column assembly ) 是由 A·沃伊塔利克 P·波尼基耶夫斯基 D·克里梅克 L·杜季奇 于 2020-09-23 设计创作，主要内容包括：本发明公开了一种用于优化能量吸收条带的方法,所述方法包括以下步骤：生产单个金属片材,所述单个金属片材包括第一连接部分和第二连接部分,所述第一连接部分用于连接至支撑支架和车辆的固定部分中的一者,所述第二连接部分用于连接至所述支撑支架和所述车辆的固定部分中的另一者；在所述单个金属片材中生产弱化部来将所述第一连接部分与可撕裂部分隔开；弯曲所述单个金属片材的一部分,以产生将所述第二连接部分和所述可撕裂部分相互连接的弯曲部分,所述第二部分相对于所述可撕裂部分向后弯回；其中,所述步骤被选择成产生所期望的能量吸收曲线。本发明还公开了一种用于将转向柱组件的护罩固定至车辆的支撑支架组件。(The invention discloses a method for optimizing an energy absorbing strip, the method comprising the steps of: producing a single metal sheet comprising a first connecting portion for connecting to one of a support bracket and a fixed portion of a vehicle and a second connecting portion for connecting to the other of the support bracket and the fixed portion of the vehicle; producing a weakening in the single metal sheet separating the first connecting portion from the tearable portion; bending a portion of the single metal sheet to create a bent portion interconnecting the second connecting portion and the tearable portion, the second portion being bent back relative to the tearable portion; wherein the steps are selected to produce a desired energy absorption curve. A support bracket assembly for securing a shroud of a steering column assembly to a vehicle is also disclosed.)

1. A method for optimizing an energy absorbing strip, the method comprising the steps of:

producing a single metal sheet comprising a first connecting portion for connecting to one of a support bracket and a fixed portion of a vehicle and a second connecting portion for connecting to the other of the support bracket and the fixed portion of the vehicle;

producing a weakening in the single metal sheet separating the first connecting portion from the tearable portion;

bending a portion of the single metal sheet to create a bent portion interconnecting the second connecting portion and the tearable portion, the second portion being bent back relative to the tearable portion;

wherein the steps are selected to produce a desired energy absorption curve.

2. The method of claim 1, wherein the curved portion is produced with a constant radius.

3. The method of claim 2, wherein the radius of the curved portion is the same as a natural radius of the curved portion.

4. The method of claim 2, wherein a radius of the curved portion is different from a natural radius of the curved portion.

5. The method of claim 1, wherein the curved portion is produced with a variable radius.

6. The method of claim 5, wherein the variable radius increases with increasing distance from the tearable portion.

7. The method of any preceding claim, wherein the curved portion is U-shaped or substantially U-shaped, optionally wherein the curved portion is oval or rounded oval.

8. The method of any one of claims 1 to 6, wherein the curved portion is V-shaped or substantially V-shaped.

9. A method according to any preceding claim, wherein the step of producing a weakened portion comprises forming a groove between the tearable portion and the first connection portion.

10. The method of claim 9, wherein the depth of the groove varies along the length of the groove.

11. A method according to any preceding claim, wherein the step of producing a weakened portion comprises forming a perforation between the tearable portion and the first connection portion.

12. A method according to any preceding claim, further comprising the step of selecting the grain direction of the individual metal sheets so as to influence the energy absorption curve.

13. The method of claim 13, wherein the grain direction is selected to be aligned or substantially aligned with a tearing direction of the tearable portion, or wherein the grain direction is selected to be perpendicular or substantially perpendicular to the tearing direction of the tearable portion.

14. A method according to any preceding claim, further comprising the step of twisting the second connection portion to form a twist.

15. A support bracket assembly for securing a shroud of a steering column assembly to a vehicle, the support bracket assembly comprising:

a support bracket configured to be securable to the shroud; and

an energy absorbing strap for interconnecting the support bracket and a stationary portion of the vehicle;

wherein the energy absorbing strip is formed from a single metal sheet and comprises:

a first connecting portion configured to be connected to one of the support bracket and a fixed portion of the vehicle;

a tearable portion extending along a portion of one edge of the energy absorbing strip, the tearable portion being connected to the first connection portion of the energy absorbing strip by a weakened portion;

a second connecting portion configured to be connected to the other of the support bracket and a fixed portion of the vehicle; and

a curved portion interconnecting the second connecting portion and the tearable portion, the second portion being bent back relative to the tearable portion.

16. The support bracket assembly of claim 15, wherein the curved portion has a constant radius.

17. The support bracket assembly of claim 16, wherein the radius of the curved portion is the same as the natural radius of the curved portion.

18. The support bracket assembly of claim 16, wherein the radius of the curved portion is different than a natural radius of the curved portion.

19. The support bracket assembly of claim 15, wherein the curved portion has a variable radius, optionally wherein the variable radius increases with increasing distance from the tearable portion.

20. The support bracket assembly of any preceding claim, wherein the curved portion is U-shaped or substantially U-shaped, optionally wherein the curved portion is oval or rounded oval, or wherein the curved portion is V-shaped or substantially V-shaped.

21. The support brace assembly of any preceding claim, wherein the weakened portion is formed as a groove between the tearable portion and the first connection portion, optionally wherein a depth of the groove varies along a length of the groove.

22. The support brace assembly of any preceding claim, wherein the weakened portion is formed as a perforation between the tearable portion and the first connection portion.

23. The support bracket assembly of any preceding claim, wherein the grain orientation of the single metal sheet is selected so as to influence the energy absorption curve.

24. The support brace assembly of claim 23, wherein the grain direction is selected to be aligned or substantially aligned with a tear direction of the tearable portion, or wherein the grain direction is selected to be perpendicular or substantially perpendicular to the tear direction of the tearable portion.

25. The support bracket assembly of any preceding claim, wherein the second connection portion comprises a twist.

Technical Field

The present invention relates to a steering column assembly that allows the steering wheel to collapse in a controlled manner in the event of a collision by controlled disengagement (break away) of a portion of the steering column assembly from a mounting bracket that secures the steering column assembly to the vehicle body. More particularly, the present invention relates to a support bracket assembly for securing a shroud of a steering column assembly to a vehicle. The invention also relates to a method for optimizing an energy absorbing strip.

Background

It is known to provide a steering column assembly including a shroud housing a steering shaft. The steering shaft connects the steering wheel to the road wheels of the vehicle, allowing the driver to rotate the steering wheel and thereby move the road wheels. This connection may be achieved by a rack and pinion gearbox and hydraulic or electric assistance may be provided in order to assist the driver. In the case of electric assist, the motor will act on the steering shaft or the steering section between the steering shaft and the road wheels to apply a torque in the same direction as the torque applied by the driver.

The shroud may not be adjustable in a simple arrangement in which the shroud is secured directly to a support bracket secured to the vehicle body, for example to a beam extending through the vehicle behind the dashboard. In other cases, the shield may be adjustable in inclination, or adjustable in elongation, or adjustable in inclination and elongation. This may be achieved by connecting the shroud to a support bracket, which in turn is fixed to the mounting bracket, by an adjustable clamping mechanism. During adjustment, the clamping assembly is loosened and the shroud may be moved up or down or along the support bracket.

To improve safety, it is known for the shield to be telescopic so that in the event of a collision in which the driver is thrown onto the steering wheel, the shield can collapse and allow the steering wheel to move with the driver. This requires that the shield should normally be fixed to the vehicle body (and therefore not be able to move during normal use), but be able to disengage and move in the event of such a collision. To achieve this, it is known to use one or more break-away cartridge assemblies to secure the shield or a support bracket secured to the shield to the mounting bracket. These cartridge assemblies are designed to provide a rigid connection during normal use, but disengage when a predetermined load is applied to the cartridge assembly. Once damaged, the shield may be moved relative to the mounting bracket. An energy absorbing mechanism may be provided to absorb energy associated with the movement, thereby allowing the movement to be controlled once broken.

Disclosure of Invention

According to a first aspect, there is provided a method for optimizing an energy absorbing strip, comprising the steps of:

producing a single metal sheet comprising a first connecting portion for connecting to one of a support bracket and a fixed portion of a vehicle and a second connecting portion for connecting to the other of the support bracket and the fixed portion of the vehicle;

producing a weakening in the single metal sheet separating the first connecting portion from the tearable portion;

bending a portion of the single metal sheet to create a bent portion interconnecting the second connecting portion and the tearable portion, the second portion being bent back relative to the tearable portion;

wherein the steps are selected to produce a desired energy absorption curve.

Thus, the method enables the manufacture of the energy absorbing strip to be optimised for the desired behaviour. This allows designers and manufacturers to use a single design of energy absorbing belt for many different vehicles or for different expected impact forces, for example taking into account the mass of the driver or the expected speed of the collision.

The curved portion may be produced to have a constant radius.

The radius of the curved portion may be the same as the natural radius of the curved portion. By "natural radius", it is meant that the radius may match the radius that naturally forms during deformation of the energy absorbing strip. When the radius of the curved portion matches the natural radius, it has been found that the force deforming the energy absorbing strip is constant or substantially constant, thereby maintaining a constant energy absorbing profile.

The radius of the curved portion may be different from the natural radius of the curved portion. By "natural radius", it is meant that the radius may match the radius that naturally forms during deformation of the energy absorbing strip. When the radius of the curved portion is different from the natural radius, it has been found that the initial force to deform the energy absorbing strip is higher or lower than the force required to deform the energy absorbing strip when it has a natural radius. However, during collapse, the bend will eventually adapt such that the bend has a natural radius, at which point the force deforming the energy absorbing strip will become constant. By having a radius different from the natural radius, an energy absorption curve that varies during the collision stroke can be obtained.

The curved portion may be produced with a variable radius.

The variable radius may increase with increasing distance from the tearable portion.

The curved portion may be U-shaped or substantially U-shaped. The curved portion may be elliptical or rounded elliptical.

The curved portion may be V-shaped or substantially V-shaped.

The step of producing a weakened portion may comprise forming a groove between the tearable portion and the first connection portion. The depth and length of the grooves may be selected to help produce a desired energy absorption profile.

The depth of the groove may vary along the length of the groove.

The step of producing a weakened portion may comprise forming a perforation between the tearable portion and the first connection portion. The length, depth, frequency, and/or any other characteristic of the perforations may be selected to help produce a desired energy absorption profile.

The weakening may comprise a combination of grooves, perforations, or any other form of weakening.

The method may further comprise the step of selecting the grain direction of said individual metal sheets so as to influence the energy absorption curve. Changing the grain orientation can have a significant impact on the force required to deform the energy absorbing strips.

The grain direction may be selected to be aligned or substantially aligned with the tearing direction of the tearable portion.

By "tear direction" is meant the direction along which the energy absorbing strip is deformed.

The grain direction may be selected to be perpendicular or substantially perpendicular to the tearing direction of the tearable portion.

It has been found that aligning the grains with the tear direction results in a lower force for the same displacement compared to energy absorbing strips having grains that are not aligned with the tear direction. All other things being equal, aligning the grains perpendicular to the tear direction produces the highest force required.

The method may further include the step of twisting the second connection portion to form a twisted portion. The presence of the torsion portion may enhance the connection with the support bracket. The torsion portion may be configured to align with the support bracket.

By including a twist, the connecting portion can be perfectly aligned for connection at any angle with the support bracket to which it is attached. The twist may additionally or alternatively ensure that a suitable access is provided for the connection fasteners (e.g. screws or rivets to be attached).

Another advantage of the twist is that the twist may strengthen the ribbon to reduce the risk of problems that may affect noise, vibration, or harshness (NVH).

According to a second aspect, there is provided a support bracket assembly for securing a shroud of a steering column assembly to a vehicle, the support bracket assembly comprising:

a support bracket configured to be securable to the shroud; and

an energy absorbing strap for interconnecting the support bracket and a stationary portion of the vehicle;

wherein the energy absorbing strip is formed from a single metal sheet and comprises:

a first connecting portion configured to be connected to one of the support bracket and a fixed portion of the vehicle;

a tearable portion extending along a portion of one edge of the energy absorbing strip, the tearable portion being connected to the first connection portion of the energy absorbing strip by a weakened portion;

a second connecting portion configured to be connected to the other of the support bracket and a fixed portion of the vehicle; and

a curved portion interconnecting the second connecting portion and the tearable portion, the second portion being bent back relative to the tearable portion.

The support bracket provided by the second aspect can be adjusted to have an energy absorption profile desired by the manufacturer and therefore may be suitable for many uses.

The curved portion may have a constant radius.

The radius of the curved portion may be the same as the natural radius of the curved portion.

The radius of the curved portion may be different from the natural radius of the curved portion.

The curved portion may have a variable radius.

The variable radius may increase with increasing distance from the tearable portion.

The curved portion may be U-shaped or substantially U-shaped. The curved portion may be elliptical or rounded elliptical.

The curved portion may be V-shaped or substantially V-shaped.

The weakening may be formed as a groove between the tearable portion and the first connection portion.

The grain direction of the individual metal sheets can be selected so as to influence the energy absorption curve.

The grain direction may be selected to be aligned or substantially aligned with the tearing direction of the tearable portion.

The grain direction may be selected to be perpendicular or substantially perpendicular to the tearing direction of the tearable portion.

The second connection portion may include a torsion portion. The torsion portion may be configured to align with the support bracket.

Drawings

Specific embodiments will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a steering column assembly including a support bracket assembly of the first aspect;

FIG. 2 is a perspective view of the support bracket assembly of FIG. 1;

FIG. 3 is a perspective view of a second embodiment of an energy absorbing strap; FIG. 4 is a perspective view of the energy absorbing strap of FIG. 3 after energy absorption;

FIG. 5a is a photomicrograph image of the grain structure of an exemplary energy absorbing strip with the grains aligned with the tear direction of the energy absorbing strip;

FIG. 5b is a photomicrograph image of the grain structure of an exemplary energy absorbing strip with the grains aligned perpendicular to the tear direction of the energy absorbing strip;

FIG. 6 is a graph showing a comparison of crush force versus distance for an energy absorbing strip having the grain structure of FIGS. 4 and 5;

7 a-7 c illustrate the change in radius of the curved portion of an exemplary energy absorbing strip during deformation; and

fig. 8a to 8c show the variation of the load for the displacement of three embodiments of the energy absorbing strip, each embodiment initially having a curved portion with a different radius of curvature.

Detailed Description

Referring first to FIG. 1, a steering column assembly 100 is shown that includes a shroud 102 that houses a shaft 104. The shaft 104 is configured to attach to a steering wheel (not shown). The shaft 104 is supported by a bearing assembly 106 that allows the shaft 104 to rotate relative to the shroud 102. The support bracket 108 includes two arms 110 that depend in a generally vertical direction and provide support and stability to the shroud 102. The mounting bracket 112 is connected to the support bracket 108 by a cartridge assembly 114 located at each side of the support bracket 108. For clarity, only the mounting bracket 112 is shown in FIG. 1. The clamping assembly 116 is configured to allow the shroud 102 to move relative to the support bracket 108 in an undamped state and prevent the shroud 102 from moving relative to the support bracket 108 in a clamped state. The clamping assembly 116 is well known in the art, and thus further description of the clamping assembly is omitted for the sake of brevity.

The shroud 102 of the present embodiment is telescopically arranged with the lower shroud 118 such that the shroud 102 is adjustable relative to the lower shroud 118 and is secured in place by the clamp assembly 116. The shroud 102 may therefore be referred to as an upper shroud. The lower shroud 118 may be attached to a steering gearbox (not shown). During collapse, the shield 102 may collapse onto the lower shield 118 such that the combined length of the shield and lower shield is shortened.

Fig. 2 shows the cartridge assembly 114 in an enlarged view. The mounting bracket 112 and bolts have been omitted for clarity. The cartridge assembly 114 engages the wings 120 of the support bracket 108 and is secured to the mounting bracket 112 by bolts extending through apertures 122. This engagement with the support bracket 108 is accomplished with a frangible fastener 124 that generally holds the support bracket 108 fixed relative to the cartridge assembly 114 and the mounting bracket 112. In the event of a sufficient impact, the frangible fasteners 124 break, allowing the support bracket 108 to move relative to the cartridge assembly 114, and thus the mounting bracket 112. To control this movement, an energy absorbing strip 126 is provided on each cartridge assembly 114.

Each energy absorbing strip 126 is formed, produced (e.g., by stamping) from a single sheet of metal. The energy absorbing strap 126 includes a first attachment portion 128 attached to the cartridge assembly 114 and a second attachment portion 130 attached to the support bracket 108.

The tearable portion 132 is separated from the first connection portion 128 by a weakened portion 134 that extends approximately 90 percent of the length of the first connection portion 128. In the depicted embodiment, the weakened portion 134 is a groove through the energy absorbing strip 126. The weakened portion 134 ensures that deformation of the energy absorbing strip 126 causes the tearable portion 132 to gradually separate from the first connection portion 128 as the weakened portion 134 ruptures. The curved portion 136 interconnects the tearable portion 132 and the second connection portion 130. In this way, the energy absorbing strips 126 form a continuous sheet metal path between the first connection portion 128 and the second connection portion 130.

The first connection portion 128 is connected to the cartridge assembly 114 by a weld 138 along the length of the connection portion 128. In other embodiments, other forms of attachment may be used, such as screws, bolts, and/or rivets. The second connecting portion 130 is connected to the support bracket 108 by a fastener (in this case, the fastener is a bolt 140).

Fig. 3 shows a second embodiment of an energy absorbing strap 226. The second embodiment is identical to the first embodiment in that it also includes a first connecting portion 228, a second connecting portion 230, a tearable portion 232, a curved portion 236, and a groove 234. The illustrated first connection portion 228 includes a plurality (in this case, three) of bolt holes 242. Bolts can thus be inserted through the bolt holes 242 and the box assembly to secure the energy absorbing straps 226 to corresponding holes in the box assembly.

As shown more clearly in the embodiment of fig. 2, but also in fig. 1, the energy absorbing strip 226 includes a twist 244 on the second connection portion 230. This twist 244 ensures that the energy absorbing strip 226 conforms to the support bracket to hold the energy absorbing strip 226 securely in place during crush of the steering column assembly and consequent deformation of the energy absorbing strip 226.

As previously described, deformation of the energy absorbing straps 226 causes the weakened portions 234 to break, thereby allowing the support bracket to move relative to the mounting bracket in the longitudinal direction of the energy absorbing straps 226. As such, during deformation, the tearable portion 232 gradually deforms and bends, thereby increasing the actual length of the energy absorbing strip 226. Fig. 4 shows the energy absorbing strip 226 of fig. 3 after an impact causes it to deform.

The energy absorption profile of the energy absorbing strip (i.e., the energy absorbed at each stage of deformation) may thus be varied by varying the shape of the curved portion, the material properties of the original individual metal sheets, and/or the geometry of other portions of the design. As such, the energy absorbing strips of the depicted embodiments are highly customizable in order to obtain the energy absorption profile desired by the designer or manufacturer.

Fig. 5a and 5b show two micrographs of the grain structure of two embodiments of the energy absorbing strip. In each figure, the tear direction (which is exactly the same in each figure) is shown along with the direction of grain orientation, which is identified from the grains visible on the photomicrograph. The tear direction is along the length of the energy absorbing strip in the direction of collapse of the steering column assembly and generally aligned with the weakened portion.

In fig. 5a, it can be seen that the direction of grain orientation is parallel to the tear direction. In contrast, in fig. 5b, the grain orientation is perpendicular to the tear direction. In each case, the grain sizes are approximately the same. This difference in energy absorption curves for each energy absorbing strip can be seen in fig. 6, since the energy absorbing strips of the two embodiments are identical except for the grain structure and have a shape similar to that of fig. 3.

During the first 6mm of the crush displacement, the energy absorption of the energy absorbing strip is substantially identical. This is because this part of the collapsing stroke corresponds to the bending of the curved portion before any tearing occurs. However, once tearing begins, along the length of the weakened portion, the difference in grain structure becomes apparent.

The lower trace on fig. 6 corresponds to the energy absorption curve of the energy absorbing strip of fig. 5a, and the upper trace on fig. 6 corresponds to the energy absorption curve of the energy absorbing strip of fig. 5 b. As can be seen, once the weakened portion starts to tear, the force required per millimeter of displacement to deform the embodiment with the grain aligned with the tearing direction is significantly lower (about 300N lower) than the embodiment with the grain perpendicular to the tearing direction. It is therefore clear that by controlling the grain orientation, the energy absorption curve of each energy absorbing strip can be further adjusted.

Of course, while the depicted embodiment shows only two extremes of grain orientation, aligned and perpendicular, there may be any grain orientation between these two extremes. By having a grain orientation between these two positions, an energy absorption curve between the two extremes shown in fig. 6 can be obtained.

Another way to adjust the energy absorption curve of an energy absorbing strip is to change the initial bend radius of the energy absorbing strip. The initial bend radius is the radius of the bend prior to impact and therefore when in the steering column assembly before any force has been applied to the energy absorbing strap. It should be noted that each energy absorbing strip has a natural bend radius that is affected by material properties such as, but not limited to, stiffness, material grain direction/structure, and tear energy. After the first initial tear distance, the curved portion tends to achieve a naturally stable constant radius.

Fig. 7 a-7 c illustrate the change in radius of the curved portion 336 of an embodiment energy absorbing strip 326 during deformation of the strip 326. Fig. 7a shows the initial bend radius of the curved portion 336. In this case, the bend radius is less than the natural bend radius determined by the material properties of the energy absorbing strip 326.

After the initial stage of deformation, the energy absorbing strip 326 reaches the position shown in fig. 7 b. Here, the curved portion 336 transitions between the initial bending radius and the natural bending radius and is in a transitional state. It can be seen that the bend radius begins to grow larger as the natural radius is larger than the initial bend radius.

Fig. 7c shows the energy absorbing strip 326 after further deformation. Here, the bend radius has been enlarged to a point that is now at the natural radius of the energy absorbing strip 326. The radius of any point in the deformation of the energy absorbing strip 326 has an effect on the force required to further displace the energy absorbing strip 326.

Fig. 8a depicts the force difference for the displacement distance of the energy absorbing strips of fig. 7 a-7 c. Here, it can be seen that the force required to displace the energy absorbing strips per unit length is reduced once the initial deformation in which the force is increased is exceeded. This reduction can be attributed to the increase in radius of the bend during deformation. Once the bend reaches the natural radius, the load required to further deform the energy absorbing strip is constant because the bend maintains the natural radius for the remainder of the crash stroke.

In fig. 8b, the energy absorption curve of an embodiment having an initial bending radius equal to the natural radius is shown. Here, the force required to deform the energy absorbing strip remains constant, since the radius of the curved portion does not change during the impact stroke.

In fig. 8c, the energy absorption curve of the embodiment is shown with an initial bend radius larger than the natural radius. In this case, the force required to displace the energy absorbing strips per unit length increases after the initial deformation. This increase can be attributed to a reduction in the size of the radius of the curved portion during deformation. Once the bend reaches the natural radius, the load required to further deform the energy absorbing strip is constant because the bend maintains the natural radius for the remainder of the crash stroke.

Deformation of the energy absorbing strip by tearing is a complex material phenomenon where both shearing and bending occur simultaneously. However, simple Computer Aided Engineering (CAE) methods can achieve a good level of prediction.

Dissipation of kinetic energy is achieved by plastic dissipation and material damage during shearing. The shear force level is affected by the size of the groove, while the bending force level is affected by the entire sample thickness and the width of the bend. Different combinations of groove depth/total thickness/part width can result in different loading schemes that can be optimally used in the desired design of the steering wheel column.

Prior to simulating any embodiment of the energy absorbing strip, a relevant test of the material needs to be done. At the very least, in order to provide good simulation, it is necessary to perform a tensile test and a shear test.

The ease of obtaining a computational method to optimize the shape of the energy absorbing strips makes CAE a good and repeatable method to optimize the performance of the entire assembly during prototype development.

In addition to the properties described above, the force required to tear the energy absorbing strip may be varied by varying the grain structure, grain size, grain thickness, rolling direction, or any other material property. By varying properties such as these, the tear characteristics of the energy absorbing strip can be further controlled.