Patent Publication Number: US-2005120761-A1

Title: Column assembly of a vehicle having a steering column to be locked and unlocked

Description:
BACKGROUND OF THE INVENTION  
      1) Field of the Invention  
      The subject invention relates to a column assembly of a vehicle having a steering column to be releasably locked and unlocked.  
      2) Description of Related Art  
      Various assemblies are well-known for locking a steering column. One such assembly is a lock bolt that is spring-loaded into direct or indirect releasable engagement with the steering column. Such engagement can be achieved by removable insertion of the lock bolt into a groove, a notch, teeth, or an aperture in the steering column or in a gear, plate, or other element connected to the steering column. A mechanism is normally provided for retracting the lock bolt against the spring-loaded force to unlock the steering column for vehicle operation. As is well known to those skilled in the art, the mechanism can retract the lock bolt in response to user insertion and turning of a key or in response to one or more signals from a control system coupled to an actuator driving the mechanism.  
      One concern with such steering column locks is the ability of the lock to reliably lock the steering column and protect against the lock bolt engaging and locking the steering column during vehicle operation. For example, the lock bolt of a steering column lock should be able to properly extend and engage with the steering column (or element connected thereto as described above) even when the steering column is being turned during non-operation. As another example, a familiar problem with many conventional steering column locks is the difficulty that a user experiences in turning the ignition key to unlock the column when a counteracting torque load is imparted to the column by back torque from the wheels. After the lock bolt has been inserted into the groove, notch, teeth, aperture and the like in its extended and locked position, the load from the front wheels can bind the lock bolt in this position and make it difficult to remove. Typically, the user must turn the steering wheel to release the force upon the lock bolt in order to turn the ignition key, retract the lock bolt, and thereby unlock the steering column.  
      In newer steering column locks that are not mechanically connected to an ignition lock cylinder for actuation, the lock bolt binding can be a significant problem. With the introduction in recent years of vehicle security systems in which a steering column lock is locked and unlocked by an electronic controller connected to one or more steering column lock actuators, there is little need to locate a vehicle&#39;s ignition control (e.g., switch, button, and the like) adjacent to the steering column lock. The ignition control can be directly or indirectly connected to the column lock by wiring alone, and therefore can be located almost anywhere in the vehicle. However, without the ability of a user to mechanically manipulate the lock bolt as in most older steering column lock designs described above, reliable lock bolt disengagement can be a significant problem, particularly when the lock bolt is subjected to binding forces.  
      One such way to overcome the load is by utilizing a more powerful lock bolt drive incorporating a larger motor. However, using the larger motor requires additional packaging space within the column assembly. Currently, the vehicle industry is striving to make the column assembly smaller and therefore, utilizing the larger motor is not desirable. Other methods of overcoming the load have incorporated additional mechanisms to push the lock bolt from the opposite side of the lock bolt drive. In this manner, the lock bolt drive is capable of overcoming a specific amount of force and the additional mechanism overcomes a specific amount of force such that when acting together, the lock bolt is moved to the unlocked position. However, adding additional mechanisms to overcome the load increases the packaging space required for the column assembly. Still other assemblies have attempted to use cams, pawls, and the like to reduce the load on the lock bolt. Others have attempted to design the lock bolt and the corresponding apertures in such a way that the load is minimized and overcome easier. In each of these assemblies, the load is not consistently and reliably released each time the column is locked and the assemblies do not assist in reducing the load. Further, when the column lock is not connected to the ignition control, these pawl, cams, and designs are less effective.  
      In sum, the assemblies of the prior art are characterized by one or more inadequacies. Therefore, it would be advantageous to provide a column assembly for a vehicle that reduces the load on the lock bolt consistently when the load is present to make unlocking of the steering column easier. Further, it would be advantageous to provide the assembly having fewer or smaller components, taking advantage of components that are currently existing within the column assembly, thereby reducing the packaging of the column assembly.  
     BRIEF SUMMARY OF THE INVENTION  
      The subject invention provides a column assembly of a vehicle having a steering column to be releasably locked and unlocked. The assembly includes a steering column rotatable about a central axis and a lock bolt moveable from an unlocked position to a locked position to lock the steering column against rotation. When the lock bolt is in the locked position, a load is imparted to the lock bolt restricting movement of the lock bolt from the locked position to the unlocked position. A lock bolt drive is connected to the lock bolt for moving the lock bolt from the locked position to the unlocked position. However, in the locked position, the load prevents the lock bolt drive from being able to move the lock bolt from the locked position to the unlocked position. The assembly includes a release mechanism operative to reduce the load on the lock bolt sufficiently to enable the lock bolt drive to move the lock bolt from the locked position to the unlocked position.  
      The subject invention overcomes the inadequacies that characterize the related art assemblies. Specifically, the subject invention provides a column assembly that reduces the load on the lock bolt consistently, when the load is present, to make unlocking of the steering column easier. Further, the subject invention has smaller components and takes advantage of components that are currently existing within the column assembly, which further reduces the packaging of the column assembly.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
      These and other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description and the accompanying drawings wherein:  
       FIG. 1  is a perspective view of a vehicle having a column assembly according to the subject invention;  
       FIG. 2  is a cross-sectional side view of the column assembly having a lock bolt and a lock bolt drive housed together with a release mechanism to reduce packaging of the column assembly;  
       FIG. 3  is a environmental side view of the column lock assembly having the lock bolt and the lock bolt drive housed separately from the release mechanism;  
       FIG. 4A  is an exploded perspective view of the lock bolt and the lock bolt drive of the subject invention; and  
       FIG. 4B  is an assembled perspective view of the lock bolt and the lock bolt drive of the subject invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A column assembly for releasably locking and unlocking a steering column  12  of a vehicle  14  is shown generally at  10  in  FIG. 1 . The column assembly  10  is typically formed as part of a steering system of the vehicle  14 . The steering system includes a steering column  12  rotatable about a central axis  13  for imparting a direction to the vehicle  14 . A steering wheel  15  is mounted at one end of the steering column  12  and the other end of the steering column  12  engages a drive axle  16 . The steering system may be any one of an electric power, a hydraulic, or a pneumatic steering system. As is becoming common within the vehicle industry, many steering systems are employing steer-by-wire systems. Most of the steer-by-wire systems include a steering assist mechanism for providing feedback to a driver while steering the vehicle  14 . The vehicle industry is also attempting to reduce the packaging and the size of the column assembly  10 , while also making the vehicle  14  more secure against theft. Therefore, it is advantageous to utilize existing components within the column assembly  10 , such as the steering assist mechanism to minimize the size of the column assembly  10 .  
      When the vehicle  14  is not being operated, one method for preventing theft of the vehicle  14  is to lock the steering column  12 . Once locked, the column assembly  10  will be unlocked when the vehicle  14  is properly started with a key or similar device or upon receiving a signal. In order to lock the column assembly  10 , a lock bolt  18  is moveable from an unlocked position to a locked. When in the locked position, the steering column  12  is prevented from rotating which imparts a load onto the lock bolt  18 . The load is typically imparted from the front wheels  19  of the vehicle  14  as understood by those skilled in the art. The load is preferably a side load restricting movement of the lock bolt  18  from the locked position to the unlocked position. By side load, it is to be appreciated that since the steering column  12  wants to rotate about the central axis  13 , the side load is acting against the side of the lock bolt  18 . It is to be appreciated that those skilled in the art will recognize that other forces may be present to restrict movement of the lock bolt  18  other than as described.  
      In order to move the lock bolt  18  from the locked position to the unlocked position, a lock bolt drive  20  is connected to the lock bolt  18 . However, the load acting on the lock bolt  18  prevents the lock bolt drive  20  from being able to move the lock bolt  18  from the locked position to the unlocked position. It is to be appreciated that the lock bolt drive  20  may be any type of drive, but is preferably an electric motor.  
      The assembly  10  includes a release mechanism  22  operative to reduce the load on the lock bolt  18 . The release mechanism  22  reduces the load sufficiently to enable the lock bolt drive  20  to move the lock bolt  18  from the locked position to the unlocked position. For example, if the load acting on the lock bolt  18  is 80 Newton meters (N-m), and the lock bolt drive  20  is only able to overcome 50 N-m, then the release mechanism  22  must reduce the load by 30 N-m. One way to reduce the load is to have a release drive  24  engaging one of the steering column  12  and the lock bolt drive  20  to rotate either one of the steering column  12  and the lock bolt drive  20  circumferentially to release the load. Preferably, the release drive  24  engages the steering column  12  either directly or indirectly. Since the load is being imparted due to rotation of the steering column  12  being prevented, if the steering column  12  is rotated against the load, then the load will be reduced and will enable the lock bolt drive  20  to remove the lock bolt  18 .  
      Preferably, the release drive  24  is coupled to the particular steering system of the vehicle  14  and utilizes components currently existing in the column assembly  10 . This allows for a more compact design of the column assembly  10  since no additional components are being added. Further, since the release drive  24  is reducing the load on the lock bolt  18 , the lock bolt drive  20  is able to be smaller and more compact, which further minimizes the size of the column assembly  10 . The release drive  24  may be an electric motor used as the steering assist mechanism in the electric power steering system, a hydraulic motor used in the hydraulic steering systems, or a pneumatic motor used in the pneumatic steering system. It is to be understood that any one of the motors may be replaced with an equivalent device separate from the steering system, while still reducing the load on the steering column  12  sufficiently to enable removal of the lock bolt  18 .  
      Referring to  FIGS. 4A and 4B , the lock bolt  18  and the lock bolt drive  20  are shown in an exploded view and in an assembled view, respectively. The lock bolt drive  20  includes a housing  26  having a front cover  28  and a rear cover  30  such that the lock bolt  18  extends from the front cover  28 . Housed within the housing  26  is a worm  32  and a worm gear  34  disposed between the motor and the lock bolt  18  for moving the lock bolt  18  from the locked to the unlocked position. The lock bolt drive  20  is also housed within the housing  26  and is preferably an electric motor, and more preferably a 5-ounce inch motor. The electric motor is turned on and off by a switch  36  which is connected to a power source (not shown). The power source preferably powers both the lock bolt drive  20  and the release mechanism  22 , however, it is to be appreciated that each may have it&#39;s own power source. Most preferably, the power source is the battery used by the remainder of the vehicle  14  systems. The lock bolt drive  20  also includes a spring  38  biasing the lock bolt  18  outwardly from the front cover  28  and a carrier  40  for carrying the lock bolt  18  along the worm gear  34  and for transmitting movement between the locked and unlocked positions. Various bearings  42  also support the worm gear  34  to provide movement of the lock bolt  18  and an up-stop  44  prevents the lock bolt  18  from being moved to far. A switch actuator  37  is supported by the carrier  40  for actuating the switch  36 .  
      Referring to  FIG. 2 , the column assembly  10  may also include a sensor  46  in communication with the lock bolt drive  20  and the release mechanism  22  for sensing the load on the lock bolt  18 . The sensor  46  is able to detect a direction of the load, such as clockwise or counterclockwise about the central axis  13 , on the lock bolt  18 . Preferably, the sensor  46  is positioned adjacent the steering column  12  to sense the load, however, it may be positioned elsewhere so long as it is capable of sensing the load. Upon detection of the load, the sensor  46  transmits a signal to a processor  48 . The processor  48  is in communication with the sensor  46 , the lock bolt drive  20 , and the release mechanism  22  and coordinates operation of the lock bolt drive  20  and the release mechanism  22  to release the load. The processor  48  is preferably included with the vehicle&#39;s  14  electronics that are used to run the remainder of the vehicle&#39;s  14  systems as is known to those skilled in the art. If the sensor  46  detects a clockwise load on the lock bolt  18 , then the processor  48  directs the release mechanism  22  to rotate in a counterclockwise direction to reduce the load and vice versa for the counterclockwise load. If the sensor  46  is not utilized, then the release mechanism  22  may rotate the steering column  12  in both the clockwise and counterclockwise direction until the load is reduced to allow removal of the lock bolt  18 . Other loads may be present other than the clockwise and counterclockwise loads depending upon the specific configuration of the lock bolt  18 , the lock bolt drive  20 , and the release mechanism  22 , so long as the loads prevent the lock bolt  18  from being moved to the unlocked position.  
      In one embodiment, shown in  FIGS. 1 and 2 , the release mechanism  22  further includes a worm  50  disposed between the release drive  24  and the steering column  12  for rotating the steering column  12  circumferentially. The worm  50  extends from the release drive  24  and engages a worm gear  52  disposed between the worm  50  and the steering column  12 . The worm gear  52  defines a plurality of holes  54  spaced circumferentially about the worm gear  52  for receiving the lock bolt  18  in the locked position. Preferably, the housing  26  of the lock bolt drive  20  is housed within the column assembly  10  along with the release mechanism  22  such that packaging space and size of the column assembly  10  is reduced within the vehicle  14 .  
      In another embodiment shown in  FIG. 3 , the steering column  12  defines a plurality of apertures  56  for receiving the lock bolt  18 . In other words, the lock bolt  18  directly engages the steering column  12  to prevent rotation. The plurality of apertures  56  are spaced circumferentially about the steering column  12  to allow the lock bolt  18  to be adjacent the next nearest aperture  56  when moved into the locking position. In this embodiment, the release mechanism  22  is similar to that shown in  FIG. 2 , except that the lock bolt  18  does not engage the release mechanism  22 , since it is engaging the steering column  12 .  
      In operation, when the vehicle  14  is stopped and turned off, the lock bolt drive  20  moves the lock bolt  18  to the locked position. If the lock bolt  18  does not align with one of the holes  54  or apertures  56 , the lock bolt  18  is forced into the housing  26  against the force of the spring  38 . When the steering column  12  is rotated, such as by the driver turning the steering wheel  15 , the lock bolt  18  is biased outwardly from the housing  26  and through the hole  54  or aperture  56 . Once the lock bolt  18  engages the hole  54  or aperture  56 , the steering column  12  may still want to be rotated about the central axis  13 , by either a force of the wheels  19  of the vehicle  14  in contact with the ground or by the driver. This attempted rotation causes the load to be present on the lock bolt  18 . The load is sufficient enough to prevent the lock bolt drive  20  from being able to move the lock bolt  18  to the unlocked position.  
      When the vehicle  14  is to be operated again, the steering column  12  must be unlocked. In order to unlock the steering column  12 , the load on the lock bolt  18  must be reduced sufficiently to allow the lock bolt drive  20  to move the lock bolt  18 . It is preferred that the moving of the lock bolt  18  and the reducing of the load happens simultaneously to provide most efficient operation of the vehicle  14 . However, it is to be appreciated that a delay may be present between the reducing of the load and the moving of the lock bolt  18 . In order to reduce the load, the column assembly  10  senses the load and rotates one of the steering column  12 , the lock bolt  18 , and the lock bolt drive  20  circumferentially about the central axis  13 . Once the load is sufficiently reduced, the lock bolt  18  is moved to the unlocked position and the steering column  12  is unlocked. In the most preferred embodiment, the steering column  12  is rotated circumferentially to reduce the load. Further, if the sensor  46  is not used, then the steering column  12  may be rotated both clockwise and counterclockwise until the load is overcome and the lock bolt  18  is moved to the unlocked position.  
      Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.