Patent Publication Number: US-2006005588-A1

Title: Steering lock

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a steering lock for engaging a lock bar with a steering shaft to disable steering.  
      Japanese Laid-Open Patent Publication No. 2000-225922 describes an example of a widely used mechanical steering lock for preventing automobile theft. In such a steering lock, a mechanical key is inserted in a key cylinder and turned to disengage a lock bar, which is engaged with a steering shaft, from the steering shaft. This enables the steering wheel to be turned, or the automobile to be steered. When the mechanical key is removed from the key cylinder, the lock bar is engaged with the steering shaft to disable steering. Accordingly, the turning of the steering wheel is restricted and the steering lock functions to prevent theft.  
      Japanese Laid-Open Patent Publication No. 2003-063354 describes an example of an electronic steering lock, which has been proposed in recent years to take place of mechanical steering locks. In such a steering lock, an actuator, such as a motor, drives a lock bar so that it engages a steering shaft to disable steering.  
       FIG. 4  shows a typical electronic steering lock  100 . The steering lock  100  includes a motor  110  that drives a lock bar  130  to engage the lock bar  130  with a steering shaft  120  and disable steering.  
      In an automobile incorporating the steering lock  100 , for example, when starting the engine, the steering lock  100  is in a lock state and steering is disabled. Thus, a steering lock ECU  140  controls the motor  110  to generate rotation (e.g., forward rotation) that disengages the lock bar  130  from the steering shaft  120 . As a result, the steering lock  100  enters an unlock state and steering is enabled. Movement of the lock bar  130  from a lock position, where the lock bar  130  is engaged with the steering shaft  120 , to an unlock position, where the lock bar  130  is disengaged from the steering shaft  120 , activates an unlock detection switch  141 .  
      The steering lock ECU  140  recognizes the unlock state of the steering lock  100  through the activation of the unlock detection switch  141 . Upon recognition of the unlock state, the steering lock ECU  140  stops the motor  110 . When the steering lock  100  is in the unlock state, one of the conditions for starting the engine is satisfied.  
      For example, if a door of the automobile is opened after the engine is stopped and the steering lock ECU  140  is in the unlock state, the steering lock ECU  140  controls the motor  110  to generate rotation (e.g., reverse rotation). This engages the lock bar  130  with the steering shaft  120 . As a result, the steering lock  100  enters the lock state and disables steering. Movement of the lock bar  130  from the unlock position to the lock position activates a lock detection switch  142 .  
      The steering lock ECU  140  recognizes the lock state of the steering lock  100  through the activation of the lock detection switch  142 . Upon recognition of the lock state, the steering lock ECU  140  stops the motor  110 . In the lock state, the steering lock  100  disables steering and functions to prevent theft.  
      Regardless of whether the steering lock is mechanical or electronic, when the lock bar is tightly engaged with the steering shaft, the force required to disengage the lock bar from the steering shaft (necessary disengagement force) becomes large. In a mechanical steering lock, the necessary large disengagement force may hinder the disengagement of the lock bar from the steering shaft when turning the mechanical key. In such a case, when turning the mechanical key, the steering wheel must be slightly turned to decrease the engaging force of the lock bar relative to the steering shaft. In an electronic steering lock, the large necessary disengagement force results in the need for a motor that generates a strong drive force. This leads to the employment of a large motor.  
      To reduce the necessary disengagement force, the portion of the lock bar engaged with the steering shaft may be tapered. This would ensure the disengagement of the lock bar from the steering shaft just by turning the mechanical key or just with the force of the motor. However, this may enable forcible unlocking of the steering lock. Accordingly, the tapering of the lock bar to reduce the necessary disengagement force may affect the antitheft effect of the steering lock.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a steering lock that reduces the force required to disengage a lock bar from a steering shaft without affecting the antitheft effect of the steering lock.  
      One aspect of the present invention is a steering lock for locking a steering shaft connected to a steering wheel. The steering lock includes a lock bar that engages with the steering shaft at a lock position and disengages from the steering shaft at an unlock position. A lock stopper is movably connected to the lock bar so as to enable movement of the lock bar between the lock position and the unlock position.  
      Another aspect of the present invention is a steering lock for locking a steering shaft connected to a steering wheel. The steering lock includes a lock bar that engages with the steering shaft at a lock position and disengages from the steering shaft at an unlock position. The lock bar includes a slot and is movable in a first direction between the lock position and the unlock position. A lock stopper is movably connected to the lock bar so as to enable movement of the lock bar between the lock position and the unlock position. The lock stopper is partially received in the slot and is movable in a second direction that differs from the first direction. The lock stopper includes a first restriction portion engaged with the lock bar in the slot to restrict movement of the lock bar from the lock position to the unlock position when the lock bar is engaged with the steering shaft. A second restriction portion is engaged with the lock bar in the slot to restrict movement of the lock bar from the unlock position to the lock position when the lock bar is disengaged from the steering shaft.  
      Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
       FIG. 1  is a schematic diagram showing the structure of a steering lock according to a preferred embodiment of the present invention;  
       FIGS. 2A and 2B  are schematic diagrams showing the operation of the steering lock;  
       FIGS. 3A and 3B  are schematic diagrams showing the operation of the steering lock; and  
       FIG. 4  is a schematic diagram showing an example of a steering lock in the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A steering lock  1 , for use in an automobile, according to a preferred embodiment of the present invention will now be discussed.  
      Referring to  FIG. 1 , the steering lock  1  is an electronic steering lock that uses the force generated by a motor  10  to engage a lock bar  30  with a steering shaft  20  and disable steering.  
      The motor  10  functions as a drive source for engaging the lock bar  30  with the steering shaft  20  and disengaging the lock bar  30  from the steering shaft  20 . The motor  10  is a DC motor that generates rotation in the forward direction and reverse direction. The motor  10  is connected to a transmission mechanism  11 , which transmits the rotation force of the motor  10  to a support  50 . The transmission mechanism  11  includes a reduction gear train for reducing the speed of the rotation transmitted from a drive shaft (output shaft of the motor  10 ) to a driven shaft and a gear train for converting the rotary motion of the driven shaft to linear motion of the support  50 .  
      The steering lock  1  includes a lock body  40 . The lock body  40  includes a first socket  41 , which movably receives the lock bar  30 . The first socket  41  is linear and extends in a first direction in which the lock bar  30  is engaged with and disengaged from the steering shaft  20 . The first socket  41  has an open end. The lock bar  30  received in the first socket  41  has a distal portion exposed from the lock body  40 . The distal position is directly engaged with and disengaged from the steering shaft  20 .  
      The lock body  40  also includes a second socket  42 , which movably receives a lock stopper  60 . The second socket  42  is linear and extends in a second direction, which differs from the first direction. In the preferred embodiment, the second socket  42  extends linearly along the second direction, which is perpendicular to the first direction. The lock stopper  60  received in the second socket  42  has a distal portion connected to the lock bar  30 .  
      A coil spring, or spring  43 , is accommodated in the first socket  41 . The spring  43  is located between the wall defining the first socket  41  in the lock body  40  and the basal portion of the lock bar  30 . The spring  43  urges the lock bar  30  towards the steering shaft  20 .  
      The lock bar  30  includes a slot  31  for receiving the distal portion of the lock stopper  60 . The slot  31  is defined by an inner lower surface  32  of the lock bar  30  and the wall surfaces of an engagement block  33  (engagement surface  34  and side surface  35 ), as viewed in  FIG. 1 . Tapered surfaces  36  are provided on opposite sides of the distal portion of the lock bar  30 . The tapered surfaces  36  are each formed so that the distance from the axis L 1  of the lock bar  30  decreases in a linear manner as the distal end of the lock bar  30  becomes closer. The angle θ 1  between the axis L 1  and each tapered surface  36  is set to  45  degrees or less. In the preferred embodiment, the angle θ 1  is set to  20  degrees. The axis L 1  of the lock bar  30  extends parallel to the first direction.  
      The support  50  is arranged in the second socket  42  to support the lock stopper  60 . A spring seat  51  projects toward the lock bar  30  from the distal end of the support  50 . The spring seat  51  stably supports a spring  52  arranged between the support  50  and the lock stopper  60 . The spring  52  urges the lock stopper  60  toward the lock bar  30 . A pin insertion hole  53  extends through the support  50  in a direction perpendicular to the second direction. A pin  54  is inserted through the pin insertion hole  53 . The two ends of the pin  54  are engaged with the lock stopper  60 .  
      The lock stopper  60  includes a receptacle  61  for receiving the spring  52  and the support  50 . Two opposing elongated holes  63  extend through the walls of the lock stopper  60  and into the receptacle  61  along the second direction L 2 . The two ends of the pin  54  are movably received in the elongated holes  63 .  
      A first restriction portion  62  is defined on the distal lower part of the lock stopper  60 , as viewed in  FIG. 1 . An abutment surface  64  extends along an end face of the distal part of the lock stopper  60 . An engagement piece  71  extends from the abutment surface  64 . The engagement piece  71  has a basal portion including a flush surface  72  facing away from the steering shaft  20 . The flush surface  72  is flush with an upper surface  65  of the lock stopper  60 . Further, the engagement piece  71  has a second restriction portion  73  defined by the upper part of the engagement piece  71  so as to face away from the steering shaft  20 . The second restriction portion  73  has a restriction surface  74  extending in a direction parallel to the engagement surface  34  of the engagement block  33  in the lock bar  30 . The second restriction portion  73  includes an inclined surface  75  that connects the restriction surface  74  and the flush surface  72 . The inclined surface  75  is formed so that the distance from the axis L 2  of the lock stopper  60  decreases in a linear manner toward the basal side of the lock stopper  60  from the distal side. The angle θ 2  between the axis L 2  and the inclined surface  75  is set to  45  degrees.  
      The operation of the steering lock  1  will now be discussed with reference to the drawings.  
       FIG. 2A  shows the steering lock  1  in an unlock state in which the lock stopper  60  is held at a retracted position in the slot  31  of the lock bar  30 . In this state, the engagement block  33  of the lock bar  30  is engaged with the restriction surface  74  of the second restriction portion  73  of the lock stopper  60 . Further, the lock bar  30  is located at an unlock position. In the unlock state, the second restriction portion  73  functions to restrict movement of the lock bar  30  from the unlock position to a lock position.  
      In the unlock state, the motor  10  is driven to generate rotation for moving the support  50  toward the lock bar  30  by means of the transmission mechanism  11 . This moves the lock stopper  60  forward, that is, further into the lock bar  30 . The forward movement of the lock stopper  60  disengages the restriction surface  74  from the engagement block  33 . Then, the abutment surface  64  of the lock stopper  60  abuts against the lock bar  30 , as shown in the state of  FIG. 2B .  
      In this state, the spring  43  urges and moves the lock bar  30  toward the steering shaft  20 . As a result, the engagement block  33  of the lock bar  30  comes into contact with the inclined surface  75 , as shown in the state of  FIG. 3A . In this state, the abutment surface  64  is disengaged from the lock bar  30 .  
      Subsequently, the lock stopper  60  moves further forward into the lock bar  30  until the first restriction portion  62  engages the inner lower surface  32  of the lock bar  30 . As a result, the steering lock  1  enters the lock state in which the lock bar  30  is located at the lock position, as shown in  FIG. 3B . In this state, the first restriction portion  62  functions to restrict movement of the lock bar  30  from the lock position to the unlock position. The lock stopper  60  is held at a projected position in this state.  
      When disengaging the lock bar  30  from the steering shaft  20  in the lock state of  FIG. 3B , the motor  10  is driven to generate rotation in the reverse direction. This moves the support  50  and the lock stopper  60  rearward, that is, away from the lock bar  30 , by means of the transmission mechanism  11 . As the lock stopper  60  moves rearward, the engagement block  33  of the lock bar  30  comes into contact with the inclined surface  75 , as shown in the state of  FIG. 3A . In this state, the first restriction portion  62  is disengaged from the inner lower surface  32 .  
      Further rearward movement of the lock stopper  60  moves the engagement block  33  along the inclined surface  75  against the force of the spring  43  until the engagement block  33  becomes engaged with the restriction surface  74 , as shown in the state of  FIG. 2A . Accordingly, the lock stopper  60  moves the lock bar  30  from the lock position to the unlock position.  
      The preferred embodiment has the advantages described below.  
      (1) In addition to the engagement of the lock bar  30  with the steering shaft  20 , the engagement of the lock stopper  60  with the lock bar  30  produces an antitheft effect. This allows the lock bar  30  to have the tapered surfaces  36  that adequately loosen the engagement between the lock bar  30  and the steering shaft  20 . Thus, the force required to disengage the lock bar  30  from the steering shaft  20  is reduced. Accordingly, the steering lock  1  reduces the necessary disengagement force without affecting the antitheft effect.  
      (2) In the lock state, the first restriction portion  62  restricts movement of the lock bar  30  from the lock position to the unlock position. This maintains the steering lock  1  in the lock state.  
      (3) In the unlock state, the restriction surface  74  of the second restriction portion  73  restricts movement of the lock bar  30  from the unlock position to the lock position. This maintains the steering lock  1  in the unlock state.  
      (4) The tapered surfaces  36  of the lock bar  30  ensure the disengagement of the lock bar  30  from the steering shaft  20 .  
      (5) The reduction of the necessary disengagement force shortens the time the motor  10  is activated. This improves responsiveness when starting the engine.  
      (6) The reduction of the necessary disengagement force enables the use of a smaller motor  10 . Accordingly, the size of the steering lock  1  may be reduced.  
      (7) The reduction of the necessary disengagement force enables the reduction gear train of the transmission mechanism  11  to have a smaller reduction ratio. Accordingly, the size of the steering lock  1  may be reduced.  
      (8) The lock bar  30  and the lock stopper  60  of the steering lock  1  configure a double-axis structure. In comparison with when a steering lock includes only a lock bar so as to configure a single-axis structure, the motor  10  and the transmission mechanism  11  may be arranged closer to the steering shaft  20 . This increases the antitheft effect of the steering lock  1 .  
      It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms.  
      The steering lock  1  may be configured in a manner that the second direction is not perpendicular to the first direction as long as the second direction differs from the first direction. It is only required that the steering lock  1  includes the lock bar  30  and the lock stopper  60  configuring a double-axis structure.  
      The angle θ 1  does not have to be  20  degrees as long as it is  45  degrees or less. It is not preferable for the angle θ 1  to be greater than  45  degrees since this may frequently cause tight engagement between the lock bar  30  and the steering shaft  20 .  
      The angle θ 2  does not have to be  45  degrees as long as it is less than  90  degrees.  
      Any urging means may be used in lieu of the springs  43  and  52 .  
      A coating may by applied to the surfaces of the lock bar  30  and the steering shaft  20  to reduce the necessary disengagement force.  
      Any kind of actuator may be used in lieu of the motor  10 .  
      The concavo-convex relationship of the steering shaft  20  and the lock bar  30  may be reversed.  
      The present invention may be applied to a mechanical steering lock. This would reduce the frequency in which the steering wheel would have to be slightly turned when turning a mechanical key to reduce the engagement force between the steering shaft and lock bar. As a result, convenience would be improved.  
      The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.