Vibration damper for coupling an airbag module to a vehicle steering wheel

A damper assembly configured to mount an airbag module to a steering wheel including a steering wheel armature includes a damper element configured to engage the steering wheel armature and to extend through an opening in the steering wheel armature. The damper assembly also includes a pin configured to be connected to the airbag module and a cap structure configured to extend through the opening in the steering wheel armature. The cap structure is configured to receive the pin for axial movement so that the airbag module can move axially relative to the steering wheel armature. The damper element isolates the airbag module, the pin, and the cap structure from the steering wheel armature.

TECHNICAL FIELD

The invention relates to a vibration damper for coupling an airbag module to a vehicle steering wheel.

BACKGROUND

It is desirable to eliminate or reduce steering wheel vibrations that can be felt by the driver. These vibrations can, inter alia, occur as a result of the rigid coupling of the steering wheel to the steering column. To combat this, vibration dampers can be used to avoid undesired steering wheel vibrations by adjusting the natural frequency of the overall system so that it is within an uncritical range. For example, steering wheel mounted airbag modules can be isolated from the steering wheel by vibration dampers, so that the module can be used as a damper mass that counter-oscillates vibrations imparted to the steering wheel through the steering column.

Vibration dampers for steering wheel mounted airbag modules can also be used to provide vehicle horn functionality. In this case, the airbag module can include a horn contact, with a mating contact being provided at the steering wheel structure. In doing so, however, there is a need to balance the force required for the driver to actuate the horn with the potential of the horn switch self-actuating in response to driving conditions, such as a rough road.

SUMMARY

A damper assembly configured to mount an airbag module to a steering wheel including a steering wheel armature includes a damper element configured to engage the steering wheel armature and to extend through an opening in the steering wheel armature. The damper assembly also includes a pin configured to be connected to the airbag module and a cap structure configured to extend through the opening in the steering wheel armature. The cap structure is configured to receive the pin for axial movement so that the airbag module can move axially relative to the steering wheel armature. The damper element isolates the airbag module, the pin, and the cap structure from the steering wheel armature.

According to one aspect, the damper element can be configured to engage a lower surface of the steering wheel armature, to extend through the opening in the steering wheel armature, and to have a portion that extends from the opening above an upper surface of the steering wheel armature.

According to another aspect, the cap structure can include a lower cap configured to overlie the damper element on the lower surface of the steering wheel armature. The lower cap can extend at least partially through the damper element and the opening in the steering wheel armature. The cap structure can also include an upper cap configured to overlie and engage the portion of the damper element extending above the upper surface of the steering wheel armature. The upper cap can extend at least partially through the damper element and the opening in the steering wheel armature, and can be configured to engage and lock onto the lower cap to connect the upper cap, the lower cap, and the damper element to the steering wheel armature.

According to another aspect, the damper element can isolate the airbag module from the steering wheel armature on both the upper surface and the lower surface of the armature.

According to another aspect, the pin can be configured to extend through the upper cap, the damper element, and the lower cap to connect the airbag module to the steering wheel aperture.

According to another aspect, the damper assembly can also include a spring that encircles a portion of the pin. The spring can have a lower end that engages the upper cap and an upper end that is proximate to and engages, directly or indirectly, the airbag module. The spring can allow the airbag module to move axially relative to the steering wheel armature.

According to another aspect, the damper assembly can also include a spring that encircles a portion of the pin. The airbag module can be configured to move axially relative to the steering wheel armature against the bias of the spring. The spring can allow the airbag module to function as a horn switch actuator.

According to another aspect, the damper assembly can include a retainer pin that engages retainer pin receiving structures on a lower surface of the lower cap. The retainer pin can engage a slot in the pin to secure the connection of the airbag module to the steering wheel armature.

According to another aspect, the damper element can include a base that engages the lower surface of the steering wheel armature. the lower cap can include a base that overlies the damper element base, positioning the damper element base between the lower cap base and the lower surface of the steering wheel armature.

According to another aspect, the damper element can include a plurality of ribs that extend from an upper surface of the damper element base and engage the lower surface of the steering wheel armature.

According to another aspect, the damper element can include a cylindrical sleeve that extends from upper surface of the damper element base. The sleeve can be configured to be positioned in and engage a sidewall of the opening in the steering wheel armature.

According to another aspect, the sidewall of the steering wheel armature can include a small diameter upper sidewall, a large diameter lower sidewall, and an annular shoulder that extends from the upper sidewall to the lower sidewall. The lower surface of the steering wheel armature that the damper element base engages can be the shoulder.

According to another aspect, the damper element sleeve can be configured to extend from the opening in the steering wheel armature above the upper surface of the steering wheel armature.

According to another aspect, the upper cap can be configured to support the airbag module via the spring on the upper end portion of the cylindrical sleeve of the damper element.

According to another aspect, the upper end portion of the cylindrical sleeve of the damper element can space an annular rim portion of the upper cap from the upper surface of the steering wheel armature.

According to another aspect, the upper cap can include an annular rim and a plurality of latches that extend from a lower surface of the annular rim into the cylindrical sleeve of the damper element. The lower cap can include a cylindrical pin receiving structure that extends upward from the base plate into the cylindrical sleeve of the damper element. The latches of the upper cap can engage latch windows in the pin receiving structure to connect the upper cap to the lower cap, with the annular rim of the upper cap engaging an upper end portion of the cylindrical sleeve of the damper element, and the base of the lower cap engaging the base of the damper element.

According to another aspect, a fastener can extend through aligned fastener receiving openings in the lower cap and the damper element to connect the damper assembly to the steering wheel aperture. The damper assembly can be configured so that the only component of the damper assembly in direct engagement with the fastener is the damper element.

According to another aspect, the damper assembly can be configured so that the damper element isolates the airbag module from the fastener.

According to another aspect, the fastener can include a head portion, a shoulder portion, and a threaded shank. The threaded shank can be configured to be installed in a corresponding threaded opening in the steering wheel armature, and the shoulder can be configured to engage and be tightened against the steering wheel armature.

According to another aspect, the damper element can include a sleeve portion that extends through the fastener receiving opening in the lower cap. The damper assembly can be configured so that the shoulder portion of the fastener engages the sleeve portion of the damper element. An upper end portion of the damper element sleeve can be configured to engage a lower surface of the steering wheel aperture. A lower end portion of the damper element sleeve can be configured to extend axially beyond a lower surface of the lower cap and engage the head portion of the fastener or a washer fitted onto the fastener.

According to another aspect, a steering wheel assembly can include a steering wheel comprising a steering wheel armature, an airbag module, and at least one damper assembly connecting the airbag module to the steering wheel.

DESCRIPTION

FIG.1illustrates an example configuration of a vehicle safety system10for helping to protect an occupant14of a vehicle12. The vehicle12also includes a seatbelt18for helping to restrain the occupant14in a vehicle seat28. The vehicle safety system10includes an airbag module20mounted on a steering wheel30of the vehicle12with improved vibration damping features that are described in detail herein.

The airbag module20includes an airbag22, an inflation fluid source24, such as an inflator, and a structure26, such as a housing, for supporting the airbag22and inflator24on the steering wheel30. The airbag has a stored condition, indicated generally in dashed lines at22′, in which the airbag is deflated, folded, and stored in the housing26. The housing26may include a cover50(not shown inFIG.1) that helps conceal the airbag22while in the stored condition.

The vehicle safety system10also includes sensors40, for sensing vehicle and/or occupant conditions, and an airbag control unit (“ACU)42that is connected to the sensors. The ACU42is configured to determine the occurrence of an event for which inflation of the airbag22is desired, such as a collision, in response to signals received form the sensors40. The ACU42is operative to actuate the inflator24via control wires44in response to this determination. When actuated, the inflator24inflates the airbag from the stored condition to a deployed condition illustrated generally in solid lines at22. When the inflator24is actuated, the cover moves from a closed condition helping to conceal the airbag22in the housing26to an open condition allowing the airbag to inflate and deploy from the housing.

The airbag22inflates and deploys in a direction away from the steering wheel30and generally parallel to a steering axis32of the vehicle12. In the deployed condition, the airbag22is positioned between the occupant14and the steering wheel30and between the occupant and an instrument panel34on the driver side16of the vehicle12. The airbag22, when in the deployed condition, helps absorb the forces of impacts with the airbag and helps distribute the impact forces throughout the airbag in order to cushion the occupant and provide a desired ride-down effect.

Referring toFIGS.3-5, the airbag module20includes a reaction canister60connectable with the cover50to define a housing in which the airbag22is stored in a deflated and rolled/folded condition. The airbag module20is connected to the steering wheel30, particularly to a steering wheel armature36, which forms a central structure of the steering wheel around which the steering wheel rim (seeFIG.1) extends. The armature includes a hub38configured to receive a vehicle steering shaft (not shown) in an opening that is hexagonal in the example configuration. The steering axis32thus extends centrally through the hub38.

Referring toFIG.6, the airbag module20also includes an airbag retainer70that is positioned in the reaction canister60and encircles the inflator24. The airbag retainer70impinges a mouth portion64of the airbag22against the reaction canister60and thereby retains the airbag and the inflator24in the airbag module20with a discharge portion66of the inflator positioned inside the bag. The airbag cover28can include latching heads52at a terminal end of a cover sidewall54that snap around a peripheral edge72of the airbag retainer70while positioned within the reaction canister60. The airbag module20can be held in this assembled condition by a snap-fit in which the latching heads52are maintained in the engaged condition with the airbag retainer60by a peripheral rim62of the retainer.

The airbag module20is connected to the steering wheel30by damper assemblies100that support the airbag module in a manner such that the module acts as a damper mass that counters vibrations transferred to the steering wheel from the steering column. The damper assemblies100decouple the airbag module20from a rigid connection with the steering wheel armature36so that the module can move and oscillate independently of the armature. The airbag module20thus “floats” on the damper assemblies100. In the example configuration illustrated herein, there are three damper assemblies100that connect the airbag module20to the steering wheel30.

The coupling of the airbag module20to the steering wheel armature36via the damper assemblies100is shown in greater detail inFIGS.7-9, which illustrates a damper assembly in detail. Referring to those figures, the damper assembly100includes a pin110that is installed through an opening68in the reaction canister60. The pin110includes a head112and an annular rim114, with a slot116defined between. The head112and rim114include respective flats118,120. The flat120on the rim114permits the rim to pass through an opening68in the reaction canister60. The flat118on the head112allows the head to be positioned in the airbag retainer70. By twisting the pin110, the flats118,120rotate, which causes the slot116to engage and connect with the reaction canister60. This also causes the head112to enter and engage a slot74in the airbag retainer70. In doing so, the pin110is fixed to the reaction canister60.

The pin110has a metal construction (e.g., steel) and includes a cylindrical shank122that extends from the head112and terminates with a tip124defined by a slot126. A tapered helical spring102is configured to fit over the shank122and engage a spring retaining groove104adjacent the rim114. The engagement between the spring102and the groove104can connect the spring to the pin110. This connection can, for example, be configured to be realized through a twisting of the spring102while positioned in the groove104. The pin110and the spring102therefore form an assemblage configured to connect with the airbag module20via the reaction canister60.

The damper assembly100also includes an assemblage configured to connect with the steering wheel armature36. The assemblage includes an upper cap140, a lower cap160, and a damper element180. The assemblage is configured to be installed in an opening80in the armature36. The opening80has a stepped configuration with a small diameter cylindrical upper sidewall82, a large, rectangular lower sidewall84, and an annular shoulder86that extends from the upper sidewall to the lower sidewall. The damper element180is positioned in the opening80and engages the upper sidewall82, lower sidewall84, and shoulder86.

Referring toFIGS.7-9, the upper cap140includes a disc-shaped central portion142that defines an annular rim144. A circular spring receiving groove146extends from an upper surface of the central portion142. A series of latching heads150extend from a lower surface of the central portion142, opposite the upper surface. The upper cap140has a generally rigid construction, such as a molded plastic construction. For example, the upper cap140can have an acetal plastic (polyacetal or polyoxymethylene (POM)) construction.

The lower cap160includes a generally rectangular base162with a cylindrical pin receiving structure164extending from an upper surface thereof. The pin receiving structure164includes a plurality of latch receiving windows166spaced about its circumference. A plurality of retainer pin receiving structures170extend from a lower surface172of the base162, opposite the upper surface. The lower cap160has a generally rigid construction, such as a molded plastic construction. For example, the lower cap160can have a nylon plastic construction.

The damper element180includes a generally rectangular base182with a cylindrical cap receiving sleeve184extending from an upper surface186thereof. The damper element180includes ribs that extend from the upper surface186of the base182. Some of the ribs have a generally rectangular configuration that, generally, follows the contour of the base182. An outer rib192is coextensive with and forms an outer edge194of the damper element180. An inner rib196is spaced from both the outer rib and the cap receiving sleeve184. A pair of ribs198are arc-shaped and positioned close to and following the cylindrical contour of the cap receiving sleeve184.

The damper element180has a generally soft, compliant, elastic construction. For example, the damper element180can be molded from an elastomer material. In one example configuration, the damper element can have a molded silicon rubber construction.

To assemble the upper cap140, lower cap160, and damper element180on the steering wheel armature36, the damper element is initially positioned on top of the lower cap with the pin receiving structure164extending into the cap receiving sleeve184. The assemblage of the lower cap160and damper element180are positioned in the opening80in the armature36. An outer surface of the cap receiving sleeve184engages the upper sidewall82.

The damper element base182and the lower cap base162can both be rectangular and have matching dimensions. The dimensions of the damper element base182and the lower cap base162can be configured to also match the rectangular dimensions of the lower side wall84. The outer edge194of the damper element base182can engage or partially engage the lower sidewall84. The ribs192,194, and196engage the shoulder86. Once the lower cap160and damper element180are positioned in the armature opening80, the upper cap140is installed in the pin receiving structure164so that the latching heads150engage and snap into the latch receiving windows166.

The damper assembly100is configured so that, when the upper cap140, lower cap160, and damper element180are connected to the armature36as shown inFIG.7, the damper element spaces the rim144of the upper cap from a front/upper surface90of the armature, and spaces the base162of the lower cap from a rear/lower surface92of the armature, which is defined by the shoulder86. The upper and lower caps140,160are therefore spaced axially from the upper and lower surfaces90,92of the armature36.

To mount the airbag module20to the steering wheel armature36via the damper assembly100, the spring210is positioned on the upper cap with its lowermost helical coil positioned in the spring receiving groove146. The pin110, which is pre-installed in the reaction canister60of the airbag module20is then inserted through aligned cylindrical passages in the upper cap140(passage148), the lower cap160(passage168), and the of the damper element180(passage198). When this occurs, the uppermost helical coil of the spring102can be received in, or snap into, the spring retaining groove104in the pin110.

At the same time, the shank122extends through the aligned passages148,168,198and the tip124protrudes from the rear or bottom surface172of the base162of the lower cap160so that slot126is exposed. At this point, a retainer pin210can be installed in the retainer pin receiving structures170of the lower cap to connect the pin110and the airbag module20to the steering wheel armature36via the damper assembly100. As shown inFIG.9, the retainer pin210has a generally U-shaped configuration with a pair of generally parallel legs212connected by a base214with a semi-circular configuration. The base214is received in a pin receiving structure170having a semi-circular channel that mates with the shape of the base. The legs212are received in respective pin receiving structures170with apertures through which the respective legs extend. Bent ends of the legs212help prevent removal of the retainer pin210

When the airbag module20is installed and connected on the steering wheel30via the damper assemblies100as shown inFIG.7, the module floats on the springs102. This permits the airbag module20to be pushed toward the steering wheel30against the bias of the springs102so that the module can function as a horn switch actuator. The movement of the airbag module20against the spring bias is limited by the configuration of the slot126and its interaction with the retainer pin210. At the same time, the damper assemblies100, specifically the damper elements180, isolate the airbag module20and the from the steering wheel30, the steering wheel armature36, and the steering shaft/column to which the steering wheel is connected.

As shown inFIG.7, the airbag module20is isolated by the damper element180for axial movement, as indicated by the arrows labeled A inFIG.7, as well as in directions transverse to that axis. The axial direction indicated by arrow A inFIG.7is parallel to the steering axis32, which coincides with the axis of the steering shaft/column. The damper assemblies100adjust the natural frequency of the steering wheel/steering column system so that it is within an uncritical range by using the airbag module20as a damper mass that counter-oscillates vibrations imparted to the steering wheel through the steering column.

The damper assemblies100are configured so that the mechanical interface between the steering wheel armature36and the airbag module20is only through the vibration-damping material of the damper element180. The damper element180is the only structure that engages the armature to couple the airbag module20axially to the steering wheel30. At the upper surface90of the armature36, the airbag module20is supported via the upper cap140by the cap receiving sleeve184of the damper element180. At the lower surface92of the armature36, the airbag module20is supported via the lower cap160by the ribs196on the base182of the damper element180.

Advantageously, the ribs196help improve the vibration damping capabilities of the damper assemblies100. Because the ribs196reduce the surface area of the engagement with the lower surface92of the steering wheel armature36, any forces urging the airbag module20to move the lower cap160axially toward the armature36will produce a pressure on the ribs (force per unit area) that is increased over that which would be applied if the armature engaged the entire base182of the damper element180. As a result, the damper element180is more easily deformed. The same is true with the engagement between the upper cap140and the cap receiving sleeve184, which presents a small area of engagement.

Because the damper assembly100is configured, as described above, for increases or enhances deformation in response to axial movements of the airbag module20, it will be appreciated that vibration forces will similarly produce enhanced deformation. It is this deformation that decouples the airbag module from the steering wheel30and allows it to function as a damper mass that counters vibrations applied to the steering wheel via the steering column. The damper element180, therefore improves the vibration damping characteristics of the damper assembly100.

Another configuration of the damper assembly100is illustrated inFIGS.10-13. In the example configuration ofFIGS.10-13, the airbag module20is mounted to the steering wheel armature36via the damper assembly100in a manner that is identical to that described above in regard to the example configuration ofFIGS.1-9. The configuration of the damper assembly100ofFIGS.10-13differs from the assembly illustrated inFIGS.1-9in that the assembly includes fasteners200for providing an additional connection of the damper assembly to the steering wheel30, particularly to the steering wheel armature36. In the example configuration ofFIGS.10-13, the damper assembly100includes three fasteners200for making this connection. The damper assembly100could, however, include a different number of fasteners200, i.e., greater than or less than three fasteners.

The additional connections afforded by the fasteners200can be used in scenarios where the sole connection of the airbag module20via the engagement of the pin210with the pin110might not produce a sufficiently robust and reliable connection. This can be the case, for example, in a vehicle that undergoes significant steering shaft vibrations, such as an off-road vehicle or a commercial service vehicle.

To facilitate connecting the damper assembly100to the steering wheel armature36via the fasteners200, the lower cap160and damper element180include respective openings210,212through which the fastener can extend. The number of openings210,212in the lower cap160and damper element180can correspond to the number of fasteners included in the damper assembly100. In the assembled and installed condition of the damper assembly100, the fasteners200extend through the aligned openings210,212in the lower cap160and damper element180, with washers220optionally positioned on the fasteners200.

In the example configuration ofFIGS.10-13, the fasteners200are shoulder screws, each of which includes a head portion202, a shoulder portion204, and a threaded shank portion206. In the installed condition of the damper assembly100, the head portion202engages the washer220, which is positioned against an annular portion of the lower cap160that surrounds the opening210. The shoulder portion204extends through the washer220and the aligned openings210,212in the lower cap160and damper element180. The shoulder portion204engages the steering wheel armature36.

As shown inFIG.13, the opening212in the damper element180is formed by an annular sleeve230formed as an integral portion of the damper element. The sleeve230is configured to protrude from the base182of the damper element on both sides, so that an upper portion232engages the steering wheel armature36, and a lower portion234protrudes from the lower cap160and engages the washer220/fastener200. Because the shoulder portion204engages the steering wheel armature36, the fastener200does not compress the damper element180, particularly the sleeve230. As such, while the fasteners200connect the damper assemblies100, and, thus, the airbag module20, to the steering wheel30, the airbag module remains completely isolated from the steering wheel by the damper elements180.

In the assembled and installed condition of the damper assembly100, the fastener200is connected to the steering wheel armature36through a threaded connection with the shank portion206, with the shoulder portion204tightened against the armature. The fastener200thus essentially becomes a rigid extension of the steering wheel armature36. The damper element180is the only structure of the damper assembly100that engages both the armature36/fastener200and the assemblage of the upper cap140and the lower cap160. Because the airbag module20is connected to the assemblage of the upper and lower caps140,160via the pin110, the airbag module20is completely isolated from the steering wheel armature36by the damper element180of the damper assembly100.

When the airbag module20is installed and connected on the steering wheel30via the damper assemblies100as shown inFIGS.10-13, the module floats on the springs102. This permits the airbag module20to be pushed toward the steering wheel30against the bias of the springs102so that the module can function as a horn switch actuator. The movement of the airbag module20against the spring bias is limited by the configuration of the slot126and its interaction with the retainer pin210. At the same time, the damper assemblies100, specifically the damper elements180, isolate the airbag module20and the from the steering wheel30, the steering wheel armature36, and the steering shaft/column to which the steering wheel is connected.

As shown inFIGS.10-13, the airbag module20is isolated by the damper element180for axial movement, as indicated by the arrows labeled A inFIG.10, as well as in directions transverse to that axis. The damper assembly100maintains this isolation, despite the added fasteners200, by implementing the sleeve230in the damper element180, which forms the sole fastener engaging structure of the damper assembly. The axial direction indicated by arrow A inFIG.10is parallel to the steering axis32, which coincides with the axis of the steering shaft/column. The damper assemblies100adjust the natural frequency of the steering wheel/steering column system so that it is within an uncritical range by using the airbag module20as a damper mass that counter-oscillates vibrations imparted to the steering wheel through the steering column.

Like the example configuration ofFIGS.1-9, the damper assemblies100are configured so that the mechanical interface between the steering wheel armature36and the airbag module20is only through the vibration-damping material of the damper element180. The damper element180is the only structure that engages the armature36/fastener200to couple the airbag module20axially to the steering wheel30. At the upper surface90of the armature36, the airbag module20is supported via the upper cap140by the cap receiving sleeve184of the damper element180. At the lower surface92of the armature36, the airbag module20is supported via the lower cap160by the ribs196on the base182of the damper element180.

Advantageously, the ribs196help improve the vibration damping capabilities of the damper assemblies100. Because the ribs196reduce the surface area of the engagement with the lower surface92of the steering wheel armature36, any forces urging the airbag module20to move the lower cap160axially toward the armature36will produce a pressure on the ribs (force per unit area) that is increased over that which would be applied if the armature engaged the entire base182of the damper element180. As a result, the damper element180is more easily deformed. The same is true with the engagement between the upper cap140and the cap receiving sleeve184, which presents a small area of engagement.

Because the damper assembly100is configured, as described above, for increases or enhances deformation in response to axial movements of the airbag module20, it will be appreciated that vibration forces will similarly produce enhanced deformation. It is this deformation that decouples the airbag module from the steering wheel30and allows it to function as a damper mass that counters vibrations applied to the steering wheel via the steering column. The damper element180, therefore improves the vibration damping characteristics of the damper assembly100.