The present invention relates to a drive nut a drive screw for a seat adjuster and in particular to a nut and screw of a vehicle seat assembly that provides ease of assembly and low noise during operation.
Power seat adjuster are a popular option on many automotive vehicles and are frequently offered as standard equipment on higher priced vehicles. Such power seat adjusters are primarily used on the driver's seat and sometimes, on the front passenger seat of the vehicle to provide selective horizontal fore and aft and vertical movement of the seat as well to provide a comfortable seating position to suit each occupant's preference.
Such power seat adjusters typically carry a support frame, which supports the seat bottom and in some applications the seat back of the vehicle seat. The seat support frame is mounted on first and second, spaced track assemblies, each formed of an upper track, which is connected to the seat support frame and is slidably mounted on a lower track anchored to the vehicle floor. A drive mechanism typically includes a bi-directional electric motor, which rotates a pair of drive shafts extending outward from the motor to a gear assembly or box mounted on each upper track. In one arrangement, each gearbox rotates a lead screw extending longitudinally below each upper track. A drive block is fixedly mounted to each lower track and threadingly receives the lead screw to cause reciprocal, horizontal movement of the upper track and the attached seat support frame upon selective energization of the drive motor and the drive shafts.
Similar drive mechanisms are provided for vertical (up and down) adjustment of the seat support frame and, in a seat adjuster having a seat recliner adjustment mechanism, for angularly adjusting the position of the seat back with respect to the seat bottom. The vertical drive mechanism may also include separate front and rear edge seat adjustment drive mechanisms for selectively tilting the front rear edges of the seat bottom independent of each other as well as simultaneously to raise and lower the entire vehicle seat or, in some applications, only the seat bottom or cushion.
Each vertical and recliner drive mechanism also includes a drive motor having a rotatable output shaft connected to a gear assembly either directly in the case of the front and rear vertical drive mechanisms or by means of two shafts extending a from single motor to separate gear assemblies mounted on each upper track or on the seat support frame in the case of a seat recliner drive mechanism.
As the various drive motors are mounted between the track assemblies, the drive motor output shafts and drive shafts connected thereto are typically oriented perpendicular to the axis of the associated lead screw. In order to transmit rotation and drive force between the output shaft of the drive motor and the drive shaft connected thereto to the 90 degree offset lead screw, each gear assembly box typically includes a worm gear, which is insert molded on one end of the associated lead screw. A worm is rotatably mounted in the gear box housing in meshing engagement with the worm gear and is connected to either one of the drive motor output shafts or to one of the drive shafts so as to rotate the worm gear and thereby the lead screw upon bi-directional energization of the selective drive motor. Thus, each drive motor requires a separate gear assembly for each lead assembly for each lead screw driven by the drive motor.
The rigid connection between the gears in the gear assembly, the drive shaft motor output shaft, the drive shaft, the lead screw and drive block also leads to additional problems during assembly and operation of a power seat adjuster. It is inevitable in the manufacture assembly of a mechanical mechanism, such as power seat adjuster, that dimensional conditions, such as concentricity, TIR, and linear discrepancies from nominal design dimensions, can and typically do occur. These dimensional conditions, without correction, can cause various problems in the operation of the power seat adjuster, such as poor breakaway from a stop position, slow operation of the power seat adjuster in extreme temperatures, excessive wear of the components of the power seat adjuster, uneven operation of the power seat adjuster.
Another aspect of a power seat adjuster, which is critical in the use of a power seat adjuster, particularly during excessive forces generated during a vehicle collision, is the requirement for seat integrity. As the occupant's seat belt is frequently attached by a seat belt buckle mounting bracket directly to one of the upper tracks of a power seat adjuster to enable the seat belt to move fore and aft with the upper track, any forces exerted on the occupant during a vehicle collision are transmitted directly though the seat belt buckle mounting bracket to the upper track. These forces cause the upper track to move upward with respect to the lower track and, in the event of excessive force, could lead to a complete pullout or separation of the upper track and the attached seat from the lower track. In order to prevent track separation, seat integrity requirements have necessitated the design of the components of a power seat adjuster to resist track separation.
Several attempts have been made to provide adapters that meet the above requirements. For example, in U.S. Pat. Nos. 5,172,601, 5,467,957, and 5,575,531, a drive nut with a pair of opposing flat sided legs with rounded edges that engages a bracket having wings with a pair of opposing open ended keyhole slots is disclosed. The slots have an arcuate portion in communication with a pair of opposing flat sides. The legs are inserted into slots and then rotated so that the rounded edges of the legs engage the arcuate portion of the slots. However, the load carrying capability of the wings is reduced because of the size of the opening in the slots required to insert the legs. As a result, these designs are not always able to resist separation forces on the seat and are prone to structural failure by allowing the slots to bend and the legs to separate from the slots causing separation of the seat.
Another attempt to solve the above problem is shown in U.S. Pat. No. 5,860,319. This design uses a round block drive device to fit into a housing. A resilient member is used to cushion or isolate the drive block from the housing. The resilient member co-acts with holes formed in the side walls of the housing to permit relative motion of the threaded interconnected lead screw and drive block with the housing. This design is expensive and difficult to assembly and has not been widely used in vehicle seat applications.
Thus, the vehicle seat assemblies and, in particular seat assemblies having power adjustment capability, it is desirable to provide an adjuster, which produces low noise, emissions during operation prevents seat separation and is simple and inexpensive to make. Furthermore, it is desirable to provide an adjuster that can be easily assembled to reduce assembly time and errors.
The present invention seeks to solve most of the above problems with a simple, quiet, easy to assemble drive nut that is structurally superior to known present designs.
A vehicle seat linkage assembly including a threaded rod defining a longitudinal axis. The linkage includes a first link having a portion forming an enclosed aperture. A second link is adjacent but spaced away from the first link. The second link having a portion forming a slot. The slot has a circular portion. The circular portion and the enclosed aperture define a lateral axis extending between the first link and the second link. Additionally, a drive nut threadably engages the rod. The drive nut has one lateral projection, another lateral projection opposite the one projection and a portion engaging the rod. The drive nut and rod are moveable so that the longitudinal axis is positioned relative to the lateral axis to insert the one projection into the slot and to position the another projection adjacent but spaced away from the aperture while the one lateral projection remains in the slot. The another projection has a width substantially the same as the base of the aperture. Thereafter moving the another projection relative to insert the another projection into the aperture while the one lateral projection remains in the slot.
The present invention is advantageous in that the drive nut engages a slot on one side and an aperture on the other side so that the drive nut is prevented from being withdrawn from the slot and the aperture. Furthermore, the drive nut is easy to assemble, inexpensive to make and produces law noise.
From the foregoing disclosure and the following more detailed description of the various preferred embodiments, it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology and art of vehicle seat linkage assemblies. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the seat adjuster assembly as disclosed here, including, for example, specific dimensions of the drive nut and its associated bracket, will be determined in part by the particular intended application and use environment. Certain feature of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity of illustration. All references to direction and position, unless otherwise indicated, refer to the orientation of the drive member in the seat structure illustrated in the drawings.