Active anti-bunching D-ring seat belt system

A motor vehicle seat belt system having an active system for avoiding bunching of webbing in a D-ring during a rapid deceleration event. The system includes a controlled locking mechanism engageable with a rotatably mounted D-ring to restrict backward rotation of the D-ring.

BACKGROUND

This invention relates to automotive safety restraint systems and, in particular, to an active three-point seat belt system with a D-ring rotation restraint.

Numerous designs of passive and active automotive occupant restraint systems are known for enhancing occupant protection in the event of a vehicle crash. Passive systems such as inflatable restraints or air bags and automatically deployed seat belt systems are known. Active seat belt systems have been used for many decades and are manually deployed by the occupant. The conventional seat belt system uses three points of connection with the vehicle structure and incorporates a lap belt section for restraining the occupant's lower torso and a shoulder belt section for restraining the occupant's upper torso. The seat belt restrains movement of the occupant in the event of a vehicle impact or rollover event. In order to enhance the comfort and convenience provided by the seat belt system, retractors are normally used which permit the belt webbing to be extracted and retracted onto the retractor, allowing movement of the occupant while maintaining the belt in close contact with the occupant. An inertia sensitive actuator locks the retractors when an impact or rollover event is detected, preventing extraction of webbing.

A seat belt system may use a three-point restraint system having a fixed upper shoulder belt anchorage. More commonly, however, the shoulder portion of the seat belt webbing extends from a retractor mechanism secured to the interior of the vehicle, most often near the lower portion of the “B-pillar” with the lower end of the bolt attached to a fixed exchange or a second belt retractor. In such installations, the webbing undergoes a sharp bend and slides through and a narrow slotted opening in a “turning loop” or D-ring for extending down and across the occupant's torso to a tongue latch. The seat belt system is engaged when the occupant inserts the latch into a buckle. The D-ring may be attached to a height adjustment mechanism installed in the B-pillar in order to comfortably accommodate the size and height of the occupant. To facilitate extraction and retraction of the webbing as well as to maximize occupant comfort, the D-ring rotates about an axis defined by a fastener mounted to the height adjustment mechanism and the B-pillar.

When the vehicle rapidly decelerates, such as during a collision, the seat belt webbing may stretch, its edges may curl, and it may slide laterally forward and bunch up in the corner of the slotted opening in the D-ring, a condition known as bunching. As the webbing collects in the corner of the D-ring, the deceleration forces acting through the webbing on the D-ring tend to cause the leading edge of the D-ring to rotate downwards and backwards. As the webbing collects, or bunches, the tension forces exerted on the webbing are concentrated in the leading corner of the D-ring rather than distributed evenly across the entire length of the D-ring slotted opening. The bunching can also cause uneven loads on the webbing itself and can interfere with further controlled extraction of webbing desirable for load limiting operation, or belt restriction for belt tensioning as the slotted opening restricts movement of the bunched portion of the webbing.

It would be desirable to have a system which permitted the D-ring to rotate freely in order to accommodate extraction and retraction of webbing when the occupant attaches and detaches the seat belt, but which restricts backward rotation of the D-ring during a rapid deceleration to minimize bunching of the webbing.

SUMMARY OF THE INVENTION

The present invention is an active system which prevents the D-ring from rotating backwards in a rapid deceleration event. In one embodiment, an active seat belt assembly includes a D-ring and a controlled locking mechanism engagable with the D-ring for restricting its backward rotation. In another embodiment, the locking mechanism comprises a locking pin operated by an electric solenoid which engages the locking pin when signaled by a controller or electrical signal. In another embodiment, the solenoid engages the locking pin when the tongue of the seat belt latch is inserted into the buckle. When the occupant unlatches the seat belt buckle in said embodiment, a spring disengages the locking pin thereby permitting the D-ring to rotate backwards and the webbing to retract smoothly into the retractor mechanism.

Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the embodiments and the appended claims, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention or its application or uses.

The present invention is an active three point automotive seat belt system to restrict the backward rotation of a D-ring to minimize bunching of webbing during a rapid deceleration event.FIG. 1shows three point seat belt system10in a typical installation in an automotive vehicle to protect an occupant seated in seat12. Seat belt system10principally comprises shoulder retractor14and webbing16. In one typical installation, shoulder retractor14is installed at or near the base of B-pillar24of the vehicle. Webbing16extends from shoulder retractor14and passes through a turning loop, or D-ring18mounted to the vehicle body, typically on or near the B-pillar24. D-ring18is commonly rotatably attached to a vertically adjustable mounting unit40attached to B-pillar24above shoulder retractor14and above and behind the outside shoulder of the seat occupant. Seat belt system10is deployed when the occupant grasps and inserts tongue20into buckle22securing them together by “latching” the seat belt. A torsion spring within shoulder retractor14takes up slack in the other end of webbing18as the occupant deploys the system. Shoulder retractor14anchors the upper portion of webbing16.

In one preferred embodiment of the system10, tongue20is permitted to freely slide along webbing16. The lap belt section of webbing16extends from tongue20, passes across the lap of an occupant and terminates at or near the floor of the vehicle at a lower anchorage position.FIG. 1shows a single retractor system, where the lap belt section is anchored to the vehicle frame, or possibly to the seat frame structure. Depending on the application, it may be preferable to have two webbing retractors in addition to shoulder retractor14, the end of the lap belt section of webbing16may be attached to a lap retractor (not shown) installed near the floor of the vehicle proximate to the lower torso region of the occupant. In a dual retractor installation, tongue20ordinarily does not slide freely along webbing16, but rather is fixed to the ends of the lap belt and shoulder sections of webbing16.

In some vehicle installations, shoulder retractor14, buckle22, and the terminal end of the lap belt section are all mounted to the vehicle frame, with D-ring18mounted to the B-pillar24. Some vehicles available today feature so-called integrated structural seats, which have sufficient internal structural integrity to permit shoulder retractor14, buckle22, and the terminal end of the lap belt section of the webbing to be mounted to the movable part of the seat. Three point seat belt system10in accordance with this invention may be mounted in these and various other manners.

Should retractor14operates in the manner of so-called emergency locking retractors in which a torsion spring provides a retraction force on the webbing16at all times. An internal saw tooth profile ratchet wheel (not shown) within the retractor engages with locking elements to prevent extraction of the webbing16during a period of rapid deceleration, such as a collision. Such events may be detected through the use of internal pendulum or ball-type inertia sensitive actuators or electronic sensing devices. Shoulder retractor14(and a lap retractor if present) may include internal mechanisms in which retraction and extension may also be controlled electronically by a controller46based on multiple sensory inputs.

FIGS. 2aand2bdepict a D-ring system as commonly deployed in the prior art. D-ring18has an oblong slotted opening30through which seat belt webbing16passes. In a typical installation, D-ring18rotates about axis32, defined by a threaded fastener or similar connector attaching D-ring18to B-pillar24along axis32. Prior to an occupant's entering the vehicle, webbing16has only slight tension, D-ring18hangs down relatively freely, and slotted opening30is typically relatively horizontal.FIG. 2ashows the position of the D-ring18and webbing16with the seat belt system deployed as the vehicle begins to rapidly decelerate, such as in hard braking or during a collision. As the motor vehicle decelerates, the momentum of the occupant exerts substantial force34on the shoulder portion of webbing16. At the same time, the shoulder retractor end of webbing16exerts on D-ring18approximately the same magnitude of force in a downward direction36. In a typical installation where shoulder retractor14is installed below D-ring18, the combination of forces acting on the webbing16and D-ring18, particularly forces34and36, combined with the stretching of the webbing16tend to cause webbing16to curl and translate forward and collect in the forward edge of slotted opening30, a condition known as D-ring bunching.

FIG. 2bshows the effect of such bunching. The bunching of webbing16at the forward edge of slotted opening30causes the forward force34exerted by the occupant and downward force36exerted by the shoulder retractor to concentrate at the leading edge of the slotted opening30. Bunching and the resultant concentrated loads on the leading corner of the D-ring has led to D-rings being designed to withstand the concentrated loading created by this condition. D-rings may be larger and bulkier than if webbing forces were more evenly distributed across the bottom of slotted opening30. Moreover, shoulder retractor14may incorporate load limitation features that permit limited extraction of webbing16during a rapid deceleration event. Bunching interferes with the smooth flow of the webbing through the D-ring opening30. Smooth flow of webbing16through slotted opening30is desirable during a rapid deceleration event to accommodate webbing stretching and/or partial webbing extraction as shoulder retractor14operates in a load-limiting mode and may also be desirable to accommodate webbing retraction through retractor tensioning operation.

FIGS. 3 and 4show a D-ring system in which a locking mechanism engages to restrict the backward rotation of D-ring18. D-ring18is shown rotatably attached to an optional vertical adjustment unit40which is in turn attached to B-pillar24by means of a threaded fastener38passing through D-ring18. Vertical adjustment unit40cooperates with an anchorage assembly and a vertical elongated track41typically having a C-shaped cross section. When a lever43on vertical adjustment unit40is depressed, vertical adjustment unit40and D-ring18become slidable up or down B-pillar24along the elongated track41.

As shown inFIGS. 3 and 4, a controllable locking mechanism42is attached to vertical adjustment unit40to restrict the range of D-ring rotation when engaged. When engaged, locking mechanism42restricts D-ring18from rotating freely backwards (away from the collision). With its rotation restricted, the orientation of slotted opening30of D-ring18remains in a position to distribute load forces34and36more evenly across slotted opening30during rapid deceleration. By assuring more even distribution of loading forces, D-ring18may be designed in ways that are more efficient and less obtrusive while providing enhanced performance.

In one embodiment, the locking mechanism is comprised of a locking pin42activated by an electric solenoid44. When provided with an appropriate signal, solenoid44will activate and pull locking pin42into a position to interfere with the rotational arc of D-ring18to restrict its range of backward pivoting rotation. Other controllable locking mechanisms include a friction brake or other electromechanical locking systems. In one embodiment, solenoid44will engage locking pin42when tongue20is inserted into buckle22, with buckle22sending a signal to controller46, which sends a signal to activate solenoid44to engage locking pin42. Alternatively, the locking mechanism could be engaged by a signal generated in response to a timer, vehicle movement, a period of rapid deceleration such as a collision, or engaged mechanically such as by the force of an occupant's weight in seat12. In another embodiment, the locking mechanism could be engaged by a direct electrical current upon latching buckle22with tongue20without intervening controller46. In these or other embodiments, the solenoid apparatus may comprise a spring or other biasing mechanism within the solenoid apparatus to disengage the locking pin from the rotation path of D-ring18when the solenoid is not powered, allowing D-ring18to rotate freely. In this embodiment, when the motor vehicle is stopped and an occupant unlatches buckle22, the solenoid will not be powered, the spring will disengage the locking pin, and D-ring18will be free to rotate to a more horizontal orientation allowing webbing16to smoothly retract and extract from shoulder retractor14.

Seat belt system10may incorporate webbing retractors such as shoulder retractor14which have internal pretensioning devices which cause slack in seat belt system10to be taken up in the event of a sensed impact, or incorporate load-limiting devices that allow webbing16to extract from a retractor in a controlled manner during a rapid deceleration event. Seat belt system10may also incorporate sensors related to transmission gear position, ignition key positions, door closure position, occupant position, or vehicle motion and acceleration. Collectively, these and similar sensors relating to vehicle operating conditions are defined as “vehicle operating sensors” in this specification and the claims. Signals sent by such sensing systems may be sent to controller46, along with the signal indicating when tongue20and buckle22are latched. Controller46could be programmed based on any combination of signals sent by these and other sensors to engage or to disengage D-ring locking mechanism42.