Patent Publication Number: US-2021188134-A1

Title: Vehicle seat assembly

Description:
TECHNICAL FIELD 
     Various embodiments relate to a vehicle seat assembly with an adjustable seat back. 
     BACKGROUND 
     A vehicle seat assembly may be provided with a mechanism for adjustment of the angle of the seat back. Examples of mechanisms may be found in U.S. Pat. Nos. 7,329,200, 7,544,143, 8,294,311, and 9,139,109, and German Patent Publication No. 102014015938. 
     SUMMARY 
     In an embodiment, a vehicle seat assembly is provided with a support frame, and a seat back frame extending from a lower region to an upper region. The lower region of the seat back frame is rotatably connected to the support frame. A seat back frame positioning assembly is connected to the support frame and the seat back frame. The seat back frame positioning assembly has an electric motor with a motor shaft. A worm is connected to the motor shaft for rotation therewith, and the worm has a helix angle of at least six degrees. A reduction gearset has a first gear driving a second gear. The first gear is in meshed engagement with the worm. The second gear is connected to the support frame. A controller is provided to control the motor such that the motor shaft rotates at a first speed and at a second speed greater than the first speed, and the upper region of the seat back frame is rotated relative to the support frame in response to rotation of the motor shaft. 
     In a further embodiment, a user interface is provided to receive a user input requesting a seat back adjustment of the upper region of the seat back. The controller is in communication with the user interface and the electric motor to control the electric motor to rotate the motor shaft at the first speed in response to the user input. 
     In an even further embodiment, the controller is in communication with the electric motor to, in response to receiving a signal from an active vehicle system with a sensor, control the electric motor to rotate the motor shaft at the second speed to rotate the upper region of the seat back frame forward relative to the support frame. 
     In an even yet further embodiment, a speed ratio of the second speed of the motor shaft to the first speed of the motor shaft is ten to one. 
     In another further embodiment, the seat back frame positioning assembly further includes a housing having a first housing portion mating with a second housing portion. The first housing portion is sized to receive the worm and at least a portion of the gearset. The second housing portion is connected to the electric motor, the first housing portion defining a first aperture sized to receive the worm therethrough. 
     In an even further embodiment, the first aperture of the first housing portion is defined by a first cylindrical surface. The second housing portion defines a protrusion with a second cylindrical surface. The first and second cylindrical surfaces mate with one another, and are co-axial with an axis of rotation of the motor shaft. 
     In another even further embodiment, the seat back frame positioning assembly includes a bearing with an inner race and an outer race. The inner race is connected via an interference fit to one of the motor shaft and the worm. The worm is positioned between the bearing and the motor. 
     In an even yet further embodiment, the first housing portion further defines a second aperture axially aligned with the first aperture, with the second aperture sized to receive and retain the outer race of the bearing. 
     In a further embodiment, the support frame has a shaft extending across and connected to the support frame, with the second gear connected for rotation with the shaft. 
     In another further embodiment, the gearset includes a third gear connected for rotation with the first gear. The third gear is in meshed engagement with the second gear. 
     In an even further embodiment, the first gear, the second gear, and the third gear are each provided as a helical gear. An axis of rotation of the second gear is parallel with an axis of rotation of the first and third gears. 
     In a further embodiment, the gearset is a planetary gearset. 
     In another embodiment, a vehicle seat assembly is provided with a support frame, and a seat back frame extending from a lower region to an upper region. The lower region is rotatably connected to the support frame such that the seat back frame rotates about a transverse axis of rotation. A seat back adjustment assembly is connected to the support frame and to the seat back frame. The seat back adjustment assembly has a brushless electric motor with a motor shaft. A worm is connected to the motor shaft for rotation therewith, and the worm has a helix angle of ten degrees or more. A gearset is provided with the seat back adjustment assembly to rotate the seat back frame between a first angular position and a second angular position relative to the support frame. 
     In a further embodiment, a controller is provided to control the electric motor to rotate the seat back frame in response to receiving a signal indicative of a user request for a seat back position adjustment. 
     In an even further embodiment, the controller controls the electric motor to rotate the seat back frame in response to receiving a signal indicative of an event from an active vehicle system. 
     In an even yet further embodiment, the controller controls the electric motor to rotate the motor shaft at a first rotational speed in response to receiving the signal indicative of the user request. The controller controls the electric motor to rotate the motor shaft at a second rotational speed in response to receiving the signal indicative of the event from the active vehicle system. The second rotational speed is greater than the first rotational speed. 
     In another even yet further embodiment, the controller controls the electric motor to rotate the seat back frame forward by nine to eighteen degrees about the transverse axis of rotation in response to receiving the signal indicative of the event from the active vehicle system. 
     In an embodiment, a method of controlling a vehicle seat assembly is provided. A seat back frame is provided with a lower region extending to an upper region, and the lower region is connected to a support frame about a transverse axis of rotation. A reduction gearset in a housing is connected to the seat back frame and to the support frame. A worm driven by an electric brushless motor is engaged with the reduction gearset. The worm has a helix angle of at least ten degrees. A bearing is positioned on a distal end of the worm within an aperture defined by the housing. In response to a first signal indicative of an event from an active vehicle system, the electric motor is controlled to rotate the worm such that the seat back frame rotates forward about the transverse axis of rotation. 
     In a further embodiment, the electric motor is controlled to rotate the worm to rotate the upper region of the seat back frame forward or aft in response to a second signal indicative of a user request for a seat back position adjustment. 
     In an even further embodiment, the electric motor is controlled to operate at a speed in response to receiving the first signal, and operate at another speed greater than the speed in response to receiving the second signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic perspective view of a vehicle seat assembly according to an embodiment; 
         FIG. 2  illustrates a front perspective view of a seat back frame positioning assembly for use with the vehicle seat assembly of  FIG. 1 ; 
         FIG. 3  illustrates an exploded view of the seat back frame positioning assembly of  FIG. 2  with a housing; 
         FIG. 4  illustrates a schematic of a housing for use with the vehicle seat assembly and seat back positioning assembly of  FIGS. 1-3 . 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present disclosure are provided herein; however, it is to be understood that the disclosed embodiments are merely examples and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure. 
       FIG. 1  illustrates a vehicle seat assembly  10 . The vehicle seat assembly  10  may be a forward passenger seat assembly or a rear passenger seat assembly, e.g. second row or third row. The vehicle seat assembly  10  has a frame  12 , or support frame  12 , that is connected to an underlying surface. The underlying surface may be the cabin floor, or may be vehicle seat tracks that are connected to the vehicle floor to allow for the seat  10  to slide forward and rearward in the vehicle. 
     The support frame  12  has first and second sides  14 ,  16 . The frame supports a seat back frame  30  for rotation relative to the support frame  12 . The seat back frame  30  and support frame  12  support cushion and trim elements. The frame  12  also supports a seat pan  18 , which may be provided with cushion and trim elements. 
     The seat back frame  30  may rotate relative to the support frame  12  to allow for adjustment of the seat back angle or recline, and may be connected to the first and second sides of the frame. The seat back frame  30  extends from an upper region  32  to a lower region  34 . The lower region  34  of the seat back frame  30  is rotatably connected to the first and second sides  14 ,  16  of the support frame  12  about a first transverse axis of rotation  36 . 
     With respect to the disclosure, a longitudinal axis  20 , a transverse axis  22 , and a vertical axis  24  are shown, and may be relative to the installation of the vehicle seat  10  in a vehicle. The axes may be orthogonal to one another. As used herein, the term substantially refers to an angle that is within five degrees of the stated angle or orientation, or within ten degrees of the stated angle or orientation; or within five percent of a dimension such as a length, or within ten percent of a dimension such as a length. 
     With reference to  FIG. 1 , the support frame  14  has a torque tube  40  or shaft  40  that is connected to the first and second sides  14 ,  16 . The shaft  40  extends transversely across the seat back frame  30 . The shaft  40  may be connected to the first and second sides  14 ,  16  of the support frame  12  such that is fixed relative to the support frame  12  and does not rotate. In further examples, the shaft  40  may be incorporated into a recline mechanism and only selectively rotated based on a release of the recline mechanism. 
     The vehicle seat assembly  10  has a seat back frame positioning assembly  50  connected to the support frame  12  and the seat back frame  30 . The assembly  50  is shown in  FIGS. 1-2  with the housing omitted. A housing  52  for the assembly  50  is described below with respect to  FIG. 3 . The assembly  50  is configured to rotate the seat back frame  30  between a first angular position and a second angular position relative to the support frame  12  and about the transverse axis  36 . 
     The assembly  50  has a prime mover  60  such as an electric motor. In various examples, the electric motor  60  is a brushless electric motor. The electric motor  60  has a motor shaft  62 . The electric motor  60  may be powered using electrical energy on-board the vehicle, e.g. from a battery. The electric motor  60  may be the sole electric motor  60  provided for the assembly  50  and be configured for both comfort adjustment of the seat back  30  by a user, and rapid repositioning of the seat back  30  based on a vehicle system input or event, as described further below. The electric motor  60  has a low mass, and has a high power output and a range of rotational speeds of the motor shaft  62 . By use of a brushless electric motor  60 , additional control may be provided with respect to the accuracy of the actuation, speed control, and response time of the motor. Additionally, a brushless motor  60  may have a higher efficiency at high power and speed outputs, as it has a reduced current draw in comparison to a conventional brush motor. 
     According to one non-limiting example, the motor  60  is controllable to operate at a first, low rotational speed, and a second, high rotational speed. The speed ratio between the second rotational speed and the first rotational speed may be ten to one. The first rotational speed may be 2000-3000 revolutions per minute (rpm). The second rotational speed may be 20,000-25,000 rpm. In other examples, other speeds and speed ratios are also contemplated for the motor. 
     A worm  64  is provided and is connected to the motor shaft  62 . The worm  64  is driven by the motor shaft  62  and rotates with and at the same speed as the motor shaft  62 . The worm  64  may be connected to the motor shaft  62  via a spline, keyway, or other similar connection. In other examples, the worm  64  may be connected to the motor shaft  62  via an interference fit. The worm  64  may be spin balanced prior to installation on the motor shaft  62 . Spin balancing of the worm  64  may be required based on the second rotational speed of the motor  60 . 
     The worm  64  may have one continuous tooth  66  or thread, and be provided as a helical gear. In other examples, the worm  64  may be multi start, such as 2-start or 3-start with two or three continuous teeth  66  or threads. The worm  64  has a helix angle. The helix angle is the angle between a helix or tooth  66  of the worm  64  and a line perpendicular to the axis of rotation  68  of the worm. The helix angle may be measured in degrees. In one example, the helix angle is at least six degrees. In a further example, the helix angle of the worm  64  is ten degrees or more. As the motor and gearset  70  rotate the shaft, the recliner mechanisms on side supports  14 ,  16  are actuated to adjust and/or lock the seat back frame  30 . Back-driving torque from the seat back frame  30  may occur for example from a load from a seat occupant during a rapid or sudden forward acceleration of the vehicle, e.g. during an event, and may be carried by the recliner mechanisms connected to side supports  14 ,  16 . In one example, the worm  64  is not self-locking, which results in a higher efficiency and the recliner mechanisms connected to the side supports  14 ,  16  carry the loads. In another example, the worm  64  is selected to be self-locking such that the reduction gearset  70  as described below cannot drive, or back-drive, the worm; and the worm  64  may be self-locking in both a static and dynamic state. For a self-locking worm  64 , the assembly  50  can move and/or hold any loads imparted to the assembly by the seat back frame  30 , and maintain a position of the seat back frame  30  relative to the support frame  12 . 
     The worm  64  is drivingly connected to a reduction gearset  70 . For the reduction gearset  70 , a rotational speed of the output shaft is less than a rotational speed of the worm  64  and electric motor  60 . The reduction gearset  70  may be a two-stage reduction gearset as shown, or may have another number or stages for reduction. The reduction gearset  70  has a first gear  72  in meshed engagement with the worm  64 . The reduction gearset  70  also has a second gear  74  connected to the support frame  12 . In the example shown, the second gear  74  is connected to the shaft  40  for rotation with the shaft. The second gear  74  may be connected to the shaft  40  via a spline, keyway, or the like. 
     In one example, and as shown, the reduction gearset  70  is provided by a worm gear  72  in meshed engagement with and driven by the worm  64 . The worm gear  72  may be provided as a worm helical gear, with helical teeth. The worm gear  72  may be provided as the first gear. The worm  64  to worm gear  72  connection may provide the first reduction stage for the gearset  70 . The axis of rotation  68  of the worm  64  and the axis of rotation  76  of the worm gear  72  are perpendicular to one another. In a further example, the worm gear  72  may be provided with helical teeth that are broadened on only one side of the worm gear  72 , which may further increase the contact area between the worm  64  and worm gear  72 , and also provide a more accurate positioning of and control of the worm gear  72  relative to the worm  64 . 
     A pinion  78  may be connected for rotation with the worm gear  72 . The pinion  78  may be provided as a third gear in the gearset  70 . The worm gear  72  and the pinion  78  may rotate together about a common axis of rotation  76 . The worm gear  72  and the pinion  78  may be rotatably connected to a shaft or rod that is connected to the seat back frame, e.g., via the housing  52 , such that the worm helical gear and pinion rotate relative to the seat back frame  30 . 
     The pinion  78  is in meshed engagement with a gear  74  such that the pinion  78  drives the gear  74 . The gear  74  may be provided as the second gear, and be connected to the shaft  40  via a spline connection or the like. In one example, the pinion  78  and gear  74  are provided as spur gears. In another example, the pinion  78  and gear  74  are provided as helical gears. The axis of rotation  76  of the pinion  78  and the axis of rotation  36  of the gear  74  may be parallel to one another as shown. The pinion  78  to gear  74  connection may provide the second reduction stage for the gearset  70 . 
     In further examples, the reduction gearset  70  may have another number or arrangement of meshed gears, or may be provided by or incorporate a planetary gearset, or the like. For example, the reduction gearset  70  as described above may be provided with an additional meshed pinion and gear to provide a third reduction stage for the gearset. 
     A bearing  80  is connected to the motor shaft or the worm  64 . The bearing  80  may be provided as a ball bearing, a needle bearing, a roller bearing, or the like. The bearing  80  has an inner race  82  and an outer race  84 . In the example shown, the inner race  82  of the bearing is connected via an interference fit, or press fit, to the end region  86  of the worm  64 . The threaded section of the worm  64  is positioned between the bearing  80  and the motor  60 . The outer race  84  of the bearing is received by the housing  52 , as described below in further detail. The end region  86  of the worm may have a seat or stepped region formed on it to provide a locating feature for the inner race  82  of the bearing. 
     A controller  90  is provided and is in communication with the motor  60  to control the motor. The controller  90  may be associated with the vehicle seat assembly  10 . The controller  90  may be connected to or in communication with other vehicle or system controllers. The controller  90  may include any number of controllers, and may be integrated into a single controller, or have various modules. Some or all of the controllers may be connected by a controller area network (CAN) or other system. It is recognized that any controller, circuit or other electrical device disclosed herein may include any number of microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof) and software which co-act with one another to perform operation(s) disclosed herein. In addition, any one or more of the electrical devices as disclosed herein may be configured to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed herein. 
     The controller  90  controls the speed and direction of rotation of the motor shaft  62 . The controller  90  controls the motor  60  to control the speed of the motor shaft  62 . In one example, the controller  90  controls the motor  60  such that the motor shaft  62  rotates at a first rotational speed and at a second rotational speed. The second rotational speed is greater than the first rotational speed. In one non-limiting example, a speed ratio of the second rotational speed of the motor shaft  62  to the first rotational speed of the motor shaft  62  is ten to one. In other examples, the speed ratio may be greater or less than ten to one. As the motor shaft  62  rotates, the worm  64  is rotated to drive the reduction gearset  70  such that the upper region of the seat back frame is rotated forward or aft relative to the support frame  12 , depending on the direction of rotation of the motor shaft  62 . 
     The controller  90  may control the motor  60  to rotate the motor shaft  62  in a first rotational direction or in a second rotational direction. The electric motor shaft  62  rotating in a first direction causes the worm  64  to rotate in the first direction, and move the upper region  32  of the seat back frame  30  forwardly relative to the support frame  12  and relative to the lower region  34  of the seat back frame. The electric motor shaft  62  rotating in a second direction causes the worm  64  to rotate in the second direction, and the upper region  32  of the seat back frame to be moved rearward relative to the support frame  12 . 
     In one example, the controller  90  may control the motor  60  such that the first speed and the second speed are constant values. In another example, the controller may control the motor  60  to a variable speed profile. In a further example, the controller  90  may control the motor  60  such that the motor speeds vary with time and are controlled to a speed profile by controlling a voltage profile of the motor  60 , or the voltage-over-time profile delivered by the controller to drive the brushless motor. The voltage profile may increase or decrease over time, and may be a linear or non-linear function. In various examples, the voltage profile is based on variations in occupant stature, the starting angle of seat back, the desired angular seat back travel, and/or the desired seat back travel time. The voltage profile may additionally be varied and controlled such that the angular travel and associated travel times of the seat back differ between a preparatory travel section through a first angular range (e.g. the first nine degrees), and a final travel section through a second angular range (e.g. the second nine degrees). Whether or not the travel should be divided into angular ranges with different voltage profiles may be determined using the vehicle sensor input and various vehicle sensor algorithms. According to one non-limiting example, the motor may be controlled to a profile as described in U.S. patent application Ser. No. 16/394,664 filed Apr. 25, 2019, the contents of which are incorporated by reference in their entirety herein. 
     By use of a brushless motor, the motor torque and motor speed may be precisely controlled over time, e.g. using the voltage profile. Use of a voltage profile minimizes disturbances or abrupt movements of the seat back for the vehicle seat occupant, while satisfying the seat back travel and speed requirements from either a user interface or vehicle system as described below. 
     A user interface  92  may be provided and be in communication with the controller  90 . The user interface  92  may be provided by buttons or switches on the vehicle seat assembly  10 , or may be provided via another vehicle user interface, such as a touch display screen. The user interface  92  receives a user input requesting a seat back adjustment of the upper region  32  of the seat back. The user interface  92  allows a user to request a seat back position adjustment, either forwardly or rearwardly, of the upper region  32  of the seat back frame  30 . In a further example, the user input may be stored in memory accessible by the controller  90 , for example, within settings associated with a predetermined seat position for a memory vehicle seat assembly. 
     The user input from the interface  92  provides a first input to the controller  90 . In one example, the controller  90  receives a signal indicative of the user input and controls the electric motor  60  to rotate the motor shaft  62  at the first rotational speed in response to the user input, and in either a first or a second rotational direction. In response to receiving an input from the user interface  92  for an adjustment of the upper region  32  of the seat back frame, the controller  90  controls the electric motor  60  to rotate the worm  64  to either move the upper region  32  of the seat back frame forwardly or rearwardly to the desired location and position. The controller  90  may move the seat back frame  30  forwardly or rearwardly between a first angular position and a second angular position, or between any two positions within a range bounded by the first and second positions. In one example, the second position is forward by nine to eighteen degrees of rotation relative to the first position. When the seat back frame  30  reaches the first position or the second position, the controller  90  stops the electric motor  60 . 
     An active vehicle system  94  may also be provided and be in communication with the controller  90 . In one example, the vehicle system  94  is an active or dynamic safety system. An active or dynamic vehicle safety system may include various vehicle systems that receive and interpret signals from on-board vehicle sensors  96  to help a driver control the vehicle. Furthermore, the vehicle safety system includes forward- and/or rearward-looking, sensor-based systems such as advanced driver-assistance systems (ADAS). An ADAS may include adaptive cruise control, collision warning, avoidance, and/or mitigation systems, and the like. The ADAS may further include sensors such as cameras, radar, LIDAR, and the like. The vehicle system  94  may provide a signal to the controller  90  when it is activated based on an event, such as a sensor  96  indicating that another vehicle is within a specified proximity of the vehicle or approaching the vehicle at more than a specified rate or speed. In a further example, the signal to the controller  90  is only provided in response to the vehicle system  94  detecting a possible frontal or rear event for the vehicle. 
     The active vehicle system  94  provides a second input to the controller  90 . In one example, the controller  90  receives a signal indicative of an event from the vehicle system  94  and controls the electric motor  60  to rotate the motor shaft  62  at the second rotational speed and in the first direction in response to the input from the vehicle system  94 . In response to receiving an input from the vehicle system  94 , the controller  90  controls the electric motor  60  to rotate the worm  64  to move the upper region  32  of the seat back frame  30  forwardly from its present position to the second position. In one example, the controller  90  rotates the seat back frame  30  from the first position to the second position. In another example, the controller  90  rotates the seat back frame  30  from an intermediate position to the second position. In a further example and if the seat back frame  30  is already in the second position, the controller  90  maintains the seat back frame  30  in the second position. The input from the vehicle system  94  may be provided by a signal from a sensor  96  associated with the system, or a signal indicative of an event from an active safety system. When the seat back frame  30  reaches the second position, the controller  90  stops the electric motor  60 . The forward positioning of the upper region  32  of the seat back frame provides a load path from an occupant of the seat into the seat back frame  30  in the longitudinal direction. In one example, controller  90  may control the electric motor  60  to rotate the seat back frame  30  forward by nine to eighteen degrees of rotation in response to receiving the signal indicative of the event from the vehicle system  94 . 
     In one example, the first speed of the electric motor  60  may provide a forward speed of the seat back frame  30  at the upper edge of the upper region  32  within the range of 15-20 mm/s, and the second speed may be within the range of 150-200 mm/s. In one example, the second speed provides for forward angular movement of the seat back frame  30  by nine to eighteen degrees within approximately 0.5-2 seconds, or in a further example, within 1.0-1.2 seconds 
       FIGS. 3-4  illustrate a schematic of a housing  52  for use with the assembly. The housing  52  has a first housing portion  100 , a second housing portion  102 , and a third housing portion  104 . In a further example, the first and third housing portions  100 ,  104  may be integrally formed. The first housing portion  100  mates with the second housing portion  102 . The third housing portion  104  also mates with the first housing portion  100  to enclose the reduction gearset  70 . 
     The first housing portion  100  is sized to receive the worm  64  and at least a portion of the gearset  70 . The first housing portion  100  defines a first aperture  110  sized to receive the worm  64  therethrough. The first aperture  110  may be defined by a first cylindrical surface  112 . 
     The first housing portion  100  also defines a second aperture  114 . The second aperture  114  is sized to receive the outer race  84  of the bearing. In one example, a collet is provided in the first housing portion  100  to retain the outer race  84  of the bearing in the second aperture  114 . The collet may be tightened about the outer race  84  of the bearing using a collar, set screw, or the like. 
     The first and third housing portions  100 ,  104  may support a shaft  116  for the worm gear  72  and pinion  78 . The worm gear  72  and pinion  78  may be supported for rotation on the shaft  116 , or may be fixed to the shaft  116 , e.g. via a spline connection, with the shaft  116  supported by bearings for rotation relative to the housing portions  100 ,  104 . The first and third housing portions  100 ,  104  also provide a pair of apertures to accommodate the shaft  40 , which is connected to the first and second sides  14 ,  16  of the support frame  12 . 
     The second housing portion  102  is connected to the electric motor  60 . The second housing portion  102  is also connected to the first housing portion  100 , for example, using a set screw  118  that aligns with a locating feature  120  and retains the second housing portion  102  to the first housing portion  100 . The second housing portion  102  defines a protrusion  122  with an outer cylindrical surface  124 . The protrusion  122  may be hollow to circumferentially surround the motor shaft  62  and/or a portion of the worm  64 . The second housing portion  102  may be directly connected to the electric motor  60 , for example, using a series of fasteners extending through corresponding bolt patterns in the second housing portion  102  and electric motor  60 . 
     The first and second cylindrical surfaces  112 ,  124  are machined or otherwise formed to mate with one another. The first and second cylindrical surfaces  112 ,  124  are co-axial with an axis of rotation  68  of the motor shaft  62  and the worm  64 . The first and second cylindrical surfaces  112 ,  124  act to locate the worm  64  relative to the worm gear  72  with a high degree of accuracy, which may be reduce noise when the motor  60  is operating at the high second rotational speed. 
     The first and second apertures  110 ,  114  of the first housing portion  100  are axially aligned with one another, and are centered on the rotational axis  68  of the motor shaft  62  and worm  64  when the housing  52  is assembled. 
     Various examples according to the present disclosure provide for a method of assembling and/or controlling a vehicle seat assembly. The method may be used to control the vehicle seat assembly  10  of  FIG. 1  according to various embodiments. The method may be implemented by a controller such as the controller in  FIG. 1 . In other examples, various steps may be omitted, added, rearranged into another order, or performed sequentially or simultaneously. 
     A seat back frame is provided with a lower region connected to a support frame about a transverse axis of rotation. The seat back frame extending from the lower region to an upper region. A reduction gearset in a housing is connected to the seat back frame and to the support frame. A worm driven by an electric brushless motor is engaged with the reduction gearset. In one example, the worm is formed with a helix angle of at least ten degrees. A bearing is positioned on a distal end of the worm within an aperture defined by the housing. 
     In response to a first signal indicative of an event from an active vehicle system, the electric motor is controlled to rotate the worm such that the seat back frame rotates about the transverse axis of rotation from a first angular position to a second angular position. In response to a second signal indicative of a user request for a seat back position adjustment, the electric motor is controlled to rotate the worm to rotate the upper region of the seat back frame forward or aft. 
     The electric motor is controlled to operate at one speed in response to receiving the first signal, and is controlled to operate at another speed greater than the one speed in response to receiving the second signal. 
     Various embodiments according to the present disclosure have associated advantages over a conventional mechanism for rotational adjustment of the seat back frame  30 . In a conventional mechanism, two motors are typically provided to operate at different speeds based on the input to the mechanism. For example, various embodiments according to the present disclosure provide a faster speed of travel for the upper region  32  of the seat back frame  30 . Back-driving torque from the seat back frame  30  during an event may be carried by the recliner mechanisms for the vehicle seat assembly. Alternatively, the worm may be self-locking to cancel or offset back-driving torque from the seat back frame  30  during an event. Furthermore the assembly according to the present disclosure may be used with a vehicle system such as ADAS, as well as to adjust the seat pan position by the user via a user interface. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention and the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention and the disclosure.