Patent Publication Number: US-2023139357-A1

Title: Blocking mechanism

Description:
TECHNICAL FIELD 
     The present invention relates to a blocking mechanism for rotationally blocking a shaft of a drivetrain of a mobility apparatus, such as motor vehicle for example. 
     TECHNOLOGICAL BACKGROUND 
     Blocking mechanisms are used, for example, as a parking brake for securing a stationary motor vehicle. In such a case, they make it possible to rotationally block a transmission shaft of the motor vehicle. Such blocking mechanisms are in particular used in motor vehicles with automatic transmission, in hybrid vehicles or electric vehicles. 
     When the blocking mechanism is activated, its components may be subject to significant loads. Thus, the components of the blocking mechanism must be able to withstand considerable force to ensure reliable blocking. 
     Blocking mechanisms are known which comprise a pawl having a locking finger and pivotably mounted on a transmission casing between a release position and a locking position in which the locking finger is inserted in a locking recess secured to, in order to rotate as one with, the transmission shaft to be blocked. The blocking mechanism further includes an actuator that moves a movable carriage which is guided in rotation on the transmission casing by means of a guide rail. The movable carriage includes a roller which interacts with a cam surface of the pawl in such a way that a translational movement of the movable carriage causes the pawl to pivot. The guide rail is a piece of stamped sheet metal. It includes, on the one hand, an attachment surface which is attached by means of attachment members, such as screws, to a surface of the transmission casing and, on the other hand, a guide surface against which the roller of the movable carriage rolls and which is substantially perpendicular to the attachment surface. However, given the manufacturing tolerances of the guide rail, the angle formed between the attachment surface and the guide surface is likely to vary around 90°. Furthermore, such a guide rail has a tendency to become deformed under the various mechanical stresses. However, it is important to ensure precise positioning of the guide surface of the guide rail relative to the pawl so as, on the one hand, to ensure reliable blocking and, on the other hand, to prevent excessively high loads from passing through the blocking mechanism and thus damaging the latter. 
     It is thus necessary to propose a blocking mechanism which is reliable, inexpensive, easy to implement and withstands high loads. 
     SUMMARY 
     One idea forming the basis of the invention is a blocking mechanism for rotationally blocking a shaft of a vehicle. 
     One idea forming the basis of the invention is a blocking mechanism which makes it possible to solve one or more technical problems encountered in the prior art, for example the abovementioned problems. 
     The invention relates to a blocking mechanism for rotationally blocking a shaft of a vehicle having at least one locking recess, the blocking mechanism comprising:
         a transmission casing;   a movable pawl comprising a locking finger, the movable pawl being pivotably mounted in a plane about a pivot axis on the transmission casing between a locking position in which the locking finger is engaged in the locking recess and a release position in which the locking finger is disengaged from said locking recess, the movable pawl comprising a cam surface,   a linear actuator which moves a movable carriage guided by a guide rail,       

     in which the movable carriage includes a cam follower capable of moving on the cam surface so as to move the movable pawl from the release position into the locking position,
         a housing formed in the transmission casing,       

     in which the guide rail is fitted in the housing so as to prevent movement of the guide rail in the plane. 
     By virtue of these features, the guide rail is kept in the housing while being prevented from deforming when the blocking mechanism goes from a release position into a locking position or vice versa. To be specific, the housing takes up the loads exerted by the movable carriage on the guide rail. Thus, precise relative positioning of the guide rail is ensured. 
     According to one embodiment, the housing is machined in dimensions selected in such a way as to secure the guide rail and prevent movement of said guide rail in any direction in the plane. 
     The term “machined housing” should be interpreted within the meaning of the invention as meaning removal of material from the transmission casing. 
     According to one embodiment, the housing has a first side wall facing and at a distance from a second side wall and a first longitudinal wall located between the first side wall and the second side wall, 
     in which the guide rail has, corresponding to the housing, a first side wall facing and at a distance from a second side wall and a first longitudinal wall located between the first side wall and the second side wall,
 
and in which the first side wall, the second side wall and the first longitudinal wall of the guide rail are in contact with the first side wall, the second side wall and the first longitudinal wall, respectively, of the housing.
 
     According to one embodiment, the housing has a second longitudinal wall facing and at a distance from the first longitudinal wall, and in which the guide rail has a second longitudinal wall facing and at a distance from the first longitudinal wall. 
     According to one embodiment, the guide rail includes only the first side wall, the second side wall, the first longitudinal wall. 
     According to one embodiment, the guide rail includes only the first side wall, the second side wall, the first longitudinal wall and the second longitudinal wall. In other words, the guide rail does not include a bottom wall or a ceiling. 
     According to one embodiment, all of the walls of the guide rail are perpendicular to the plane. 
     According to one embodiment, the first side wall, the second side wall, the first longitudinal wall and/or second longitudinal wall of the guide rail has a thickness of between 1.5 mm and 3.5 mm; preferably between 2.5 and 3 mm. 
     According to one embodiment, the housing has an opening and the guide rail has an opening, the opening in the housing and the opening in the guide rail being through openings. 
     According to one embodiment, the opening in the housing is made in at least one wall selected from: the first side wall, the second side wall, the first longitudinal wall and second longitudinal wall of the housing, preferably in the second longitudinal wall. 
     According to one embodiment, the opening in the guide rail is made in at least one wall selected from: the first side wall, the second side wall, the first longitudinal wall and second longitudinal wall of the guide rail, preferably in the second longitudinal wall. 
     According to one embodiment, the opening in the housing and the opening in the guide rail are facing one another. 
     According to one embodiment, the housing has a notch and the guide rail has a notch, the notch in the housing and the notch in the guide rail are through notches and are intended to allow the passage of the linear actuator. 
     According to one embodiment, the notch is selected from: a recess, a cut-out, an oblong hole, a groove or a slot. 
     According to one embodiment, the notch in the housing is located on the first side wall of the housing and the notch in the guide rail is located on the first side wall of the guide rail. 
     According to one embodiment, the housing has a height of between 15 mm and 30 mm. 
     According to one embodiment, the cam follower includes a movable roller capable of moving on the cam surface at the opening in the housing and at the opening in the guide rail. 
     By virtue of these features, when the movable carriage is moving relative to the guide rail, the friction forces between the movable carriage and the guide rail are reduced. Therefore, movement of the movable carriage is ensured without wear of the movable carriage or of the guide rail. 
     According to one embodiment, the movable carriage comprises a second movable roller capable of moving along the first longitudinal wall of the guide rail. 
     According to one embodiment, the guide rail comprises a non-return stop preventing the movable carriage from moving beyond said guide rail. 
     By virtue of these features, the movable carriage is kept in the housing. 
     According to one embodiment, the non-return stop is formed by the first side wall of the guide rail. 
     According to one embodiment, an attachment means attaches the guide rail to the transmission casing, the attachment means attaching the guide rail in a direction perpendicular to the plane. 
     According to one embodiment, the attachment means is selected from: a screw, a screw/nut system or an adhesive material. 
     According to one embodiment, the guide rail is made as a single piece from a bent metal strip. 
     The invention also relates to a transmission system comprising a shaft having at least one locking recess and a blocking mechanism as defined above. 
     According to one embodiment, the shaft comprises a wheel including the at least one locking recess. For example, the wheel is a ratchet wheel. 
     According to one embodiment, the wheel includes one to twelve locking recesses. 
     According to one embodiment, the plurality of recesses are spaced apart regularly from one another. 
     The invention also relates to a motor vehicle comprising a transmission system as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is an end-on view of a portion of a transmission casing comprising a housing for the guide rail according to one embodiment 
         FIG.  2    is a perspective view of  FIG.  1   . 
         FIG.  3    is an end-on view of a portion of a transmission casing comprising a housing and a guide rail according to one embodiment. 
         FIG.  4    is a perspective view of  FIG.  3   . 
         FIG.  5    is a perspective view of the guide rail shown in  FIGS.  3  and  4   . 
         FIG.  6    is an end-on view of a portion of a transmission casing comprising the blocking mechanism according to one embodiment. 
         FIG.  7    is a perspective view of  FIG.  6   . 
         FIG.  8    is a perspective view of a guide rail according to another embodiment. 
         FIG.  9    is a perspective view of a guide rail according to another embodiment. 
         FIG.  10    is a perspective view of a guide rail comprising an attachment means according to one embodiment. 
         FIG.  11    is a perspective view of a rotationally blocked shaft of a vehicle. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The mechanism for rotationally blocking a shaft of a vehicle comprises in particular: a movable pawl, a linear actuator, a movable carriage, a guide rail and a housing. The blocking mechanism is in particular intended for immobilizing a vehicle, for example a car, when it is parked. 
     The various elements of the guide mechanism according to various alternative embodiments are presented below. 
       FIGS.  1  and  2    show a transmission casing  1  comprising a housing  2  for the vehicle blocking mechanism. 
     The housing  2  is formed in the transmission casing  1 , in other words the housing is not a separate part which is attached to the transmission casing  1 . To be specific, the housing  2  is hollowed out or made directly in the thickness of a wall of the transmission casing  1 . 
     The housing  2  has a generally rectangular shape with rounded corners and comprises a first side wall  21  facing and at a distance from a second side wall  22 , a first longitudinal wall  23  facing and at a distance from a second longitudinal wall  24 , and a bottom wall  46 . 
     The housing  2  is intended to house and secure a guide rail, shown in particular in  FIGS.  3 ,  4  and  5   . 
       FIGS.  3  and  4    show a portion of a transmission casing  1  comprising the housing  2  as depicted in  FIGS.  1  and  2    and also show a guide rail  27  housed in the housing  2 . 
     The guide rail  27  has dimensions similar to the housing  2  so as to be fixedly fitted in the housing  2 , in other words the guide rail  27  follows the contour of the housing  2 . The guide rail is thus held in a static position inside the housing  2  in a plane P comprising a longitudinal direction X and a transverse direction Y transverse to the longitudinal direction X, and in an orthogonal direction O at right angles to the plane, towards the bottom wall  46 . This arrangement is particularly advantageous since the various pressures exerted on the guide rail  27  are taken up by the walls of the housing  2  and thus by the transmission casing  1 . This arrangement makes it possible to retain the dimensions of the guide rail  27 , without deformation and hence without deterioration over time. Such a guide rail is in particular shown in  FIG.  5   . 
     Like the housing  2  as shown in  FIGS.  1  and  2   , the guide rail  27  shown in  FIG.  5    has a first side wall  28  facing and at a distance from a second side wall  29  and a first longitudinal wall  30  facing and at a distance from a second longitudinal wall  31 . 
     The first  28  and second  29  side walls and said first  30  and second  31  longitudinal walls of the guide rail  27  are in contact with the first  21  and second  22  side walls and the first  23  and second  24  longitudinal walls, respectively, of the housing  2 . 
     Furthermore, the first side wall  21  of the housing  2  comprises a notch  25  intended to allow the passage of a linear actuator which is shown in  FIGS.  6  and  7   . The notch  25  has a “U” shape. 
     The first side wall  28  of the guide rail  27  comprises a notch  32  with a shape corresponding to the shape of the notch  25  in the housing  2 , as shown in  FIG.  4   . The notch  32  is intended to allow the passage of a linear actuator which is depicted in  FIGS.  6  and  7   . 
     The second side wall  22  and the second longitudinal wall  24  of the housing  2  have a shared opening  26  allowing contact between a movable carriage located in the housing  2 , shown in  FIGS.  6  and  7   , and a movable pawl located at the opening  26 , shown in  FIGS.  6 ,  7  and  11   . 
     The second longitudinal wall  31  and the second side wall  29  of the guide rail  27  have a shared opening  33  in communication with the opening  26  in the housing  2 . 
     The first side wall  28  of the guide rail  27  is a non-return stop for the movable carriage  38 , shown  FIGS.  6  and  7   , so that the movable carriage is retained in translation in the housing  2 , by the guide rail  27 . 
     The guide rail  27  serves to guide the movable carriage and ensure that it only performs the translational movement necessary to actuate a locking finger in a locking recess so that the blocking mechanism is in a locking position. The locking position allows a motor vehicle to be parked, for example. 
     The guide rail is made for example from a metal strip which is on the one hand cut so as to form the notch then bent three times along its length so as to form said walls of which it is composed. The metal strip has a rectangular shape before being bent. The metal strip, before bending, may also comprise a notch intended to form the notch in the guide rail. 
       FIGS.  6  and  7    show a partial view of a mechanism for rotationally blocking a shaft in a release position. 
     The blocking mechanism comprises the housing  2  as described in  FIGS.  1  to  4    and the guide rail  27  as described in  FIGS.  3  to  5   . The blocking mechanism further comprises a movable pawl  34  located in the transmission casing  1 . 
     The movable pawl  34  has an elongate shape and has a first end  71  and a second end  72  at a distance from the first end  71 . 
     The first end  71  makes it possible to attach the movable pawl  34  to the transmission casing  1  while allowing rotational movement of said movable pawl  34 . In other words, the movable pawl is pivotably mounted in a plane P about a pivot axis. 
     The second end  72  is located at the opening  33  in the guide rail  27  and at the opening  26  in the housing. The second end  72  comprises a cam surface  36  located on a first lateral face of the movable pawl  34 , towards the inside of the housing  2 . The second end  72  further comprises a locking finger  35  projecting towards the outside of the housing  2  from a second lateral face of the movable pawl  34 . The locking finger  35  is intended, when the blocking mechanism is triggered, to be inserted in a locking recess, shown in  FIG.  11   . The locking recess is for example located on a ratchet wheel  44  which is capable of receiving said locking finger  35 , as shown in  FIG.  11   , and which is secured to, in order to rotate as one with, the transmission shaft  60  to be rotationally blocked. 
     According to an alternative shown in  FIG.  11   , the movable pawl  34  further comprises a torsion spring  50 . The torsion spring  50  is wound at the first end  71  of the movable pawl  34 . The torsion spring  50  comprises a first end portion  51  which bears against a bearing surface of the transmission casing and a second end portion  52  which bears against a bearing surface of the movable pawl  34 . The torsion spring  50  is arranged so as to exert a return force on the movable pawl  34  so as to return same to the release position. The blocking mechanism further comprises a linear actuator  37 , shown partially in  FIG.  6   , which is attached to the transmission casing  1 . The linear actuator  37  comprises a rod  39  capable of moving in the longitudinal direction X. 
     The rod  39  extends through the notch  25  in the housing  2  and the notch  32  in the guide rail  27  as far as an internal space in the housing  2 . The rod  39  is attached to the movable carriage  38  located in the housing  2 . 
     The movable carriage  38  is intended to be guided by the guide rail  27 . 
     In the case where the movable carriage  38  is pushed back by the movable pawl  34  in a dynamic phase the movable carriage  38  comes into abutment against the first side wall  28  of the guide rail  27 , which thus forms a non-return stop for the movable carriage  38 . The movable carriage  38  is in this case pushed against the movable pawl  34  by a return force exerted by a traction spring  40  which surrounds the rod  39  and which includes a first end attached to the body of the actuator and a second end attached to the movable carriage  38 . This effect may be produced, for example, during an attempt at engagement at excessively high speed. Beyond a threshold speed, for example between 3 km/h and 5 km/h, the movable pawl  34  springs back so as to prevent engagement, the movable carriage  38  is thus pushed into abutment. 
     The movable carriage  38  further comprises a first movable roller  41  capable of moving along the first longitudinal wall  30  of the guide rail  27 . The movable carriage  38  further comprises a cam follower  42  including a second movable roller which is in contact with the cam surface  36  of the movable pawl  34  and capable of moving along this cam surface  36 . 
     The movable carriage  38  further comprises a lug  43  located at the second end of the movable pawl  34 . The lug  43  is intended to keep the movable pawl  34  in the plane P. 
     To move the movable pawl  34  into the locking position, the rod  39  of the linear actuator  37  is moved through the notch  32  in the guide rail  27  thus moving the movable carriage  38  in a longitudinal direction. The movable carriage  38  is moved from the first side wall  28  of the guide rail  27 , towards the second side wall  29 . The movement of the movable carriage  38  causes the first movable roller  41  to move along the first longitudinal wall  30  of the guide rail  27  and the cam follower  42  to move along the cam surface  36  of the movable pawl  34 . The cam surface  36  has a slope and the movable carriage  38  thus exerts, via its movement, pressure towards the cam surface  36  of the movable pawl  34 . This pressure causes a rotational movement of the second end of the movable pawl  34  towards a locking recess in such a way that the locking finger  35  becomes engaged in a locking recess present for example on a ratchet wheel as shown in  FIG.  11    so as to lock said ratchet wheel  44 . 
       FIG.  11    shows a transmission casing  1  comprising a ratchet wheel  44 . The ratchet wheel  44  has a plurality of recesses  45  spaced apart regularly from one another, all the way around the ratchet wheel  44 . Each recess  45  of the plurality of recesses has dimensions making it possible to receive the locking finger  35  of the movable pawl  34 .  FIG.  11    also shows a shaft  60  of a vehicle which is rotationally blocked by the blocking mechanism. 
     To move the blocking mechanism from the locking position into the release position, the rod  39  is moved in such a way as to move the movable carriage  38  towards the first side wall  28  until it comes into abutment against the first side wall  28  of the guide rail  27 . The locking finger  35  is disengaged from the locking recess present on the ratchet wheel  44 , which releases this ratchet wheel and thus allows rotation of the transmission shaft  60 . 
       FIGS.  8  to  10    show guide rails  27  according to several embodiments, intended to be fitted in housings of the transmission casing. 
       FIG.  8    shows a guide rail  27  intended to be fitted in a housing formed in the transmission casing. The guide rail  27  has dimensions similar to the housing in such a way as to be retained in the housing  2  by cooperation of shapes between the walls of the housing and the walls of the guide rail  27 . In this regard, the guide rail  27  has a first side wall  28  facing and at a distance from a second side wall  29  and a first longitudinal wall  30  located between the first side wall  28  and the second side wall  29 . The first side wall  28  and the second side wall  29  are curved. The first side wall  28  of the guide rail  27  comprises a notch  32 . 
       FIGS.  9  and  10    show a guide rail further comprising a groove  47  located on the edge of the first longitudinal wall  30 . 
     The groove  47  receives an attachment means  48 , for example a screw, intended to attach the guide rail  27  in an orthogonal direction O at right angles to the longitudinal direction of the first longitudinal wall  30 . 
     The housing intended to receive the guide rail in  FIGS.  8  to  10    has dimensions making it possible to receive the guide rail  27  fitted thereinside. The housing thus has four parts, namely: a bottom wall, a first side wall facing and at a distance from a second side wall and a first longitudinal wall located between the first side wall and the second side wall. The first side wall and the second side wall are respectively curved in a semi-circle complementary to one another, so as to follow the first and second side walls of the guide rail. The first longitudinal wall of the housing faces an opening made by the gap between the first side wall and the second side wall. 
     Although the invention has been described in association with a plurality of particular embodiments, it is clear that it is in no way limited to this, and that it comprises all technical equivalents of the means described, as well as their combinations, if these come within the scope of the invention. 
     Use of the verbs “comprise” or “include” and their conjugated forms does not exclude the presence of elements or steps other than those described in a claim. 
     In the claims, any reference sign between parentheses should not be interpreted as limiting the claim.