Abstract:
An improved structure for a torque sensor assembly adapted for use in a vehicle steering system and method for producing the same. According to one embodiment, the torque sensor assembly includes a housing formed from a suitable material having a cavity; at least one flux concentrator and at least one hall effect IC disposed in the cavity of the housing; and a cover secured to the housing to close the cavity in the housing in a permanent and fluid-tight manner.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to vehicle steering systems and in particular to an improved torque sensor assembly particularly adapted for use in such a vehicle steering system and method for producing the same. 
     A torque sensor assembly is well known in the art in connection with a vehicle electric steering system for the purpose of measuring the torsion of the associated steering column. Examples of know torque sensors are shown in U.S. Pat. No. 6,912,923 B2 to Froehlich, et al., U.S. Pat. No. 7,028,545 B2 to Gandel, et al., and U.S. Pat. No. 7,415,898 B2 to Ishihara et al. 
     SUMMARY OF THE INVENTION 
     This invention relates to an improved structure for a torque sensor assembly particularly adapted for use in a vehicle steering system and method for producing the same. 
     According to one embodiment, the torque sensor assembly includes a housing formed from a suitable material having a cavity; at least one flux concentrator and at least one hall effect IC disposed in the cavity of the housing; and a cover secured to the housing to close the cavity in the housing in a permanent and fluid-tight manner. In this embodiment, the cover is formed separate from the housing and is secured to the housing by laser welding. The torque sensor assembly can further include a carrier which is disposed in the cavity of the housing and the at least one flux concentrator and at least one hall effect IC are disposed in the carrier. The torque sensor assembly can further include a printed circuit board which is attached to the carrier. 
     According to another embodiment, the torque sensor assembly includes a housing formed from a suitable material having a cavity; at least one flux concentrator and at least one hall effect IC disposed in the cavity of the housing; and a cover secured to the housing to close the cavity in the housing in a permanent and fluid-tight manner. In this embodiment, the cover is formed as part of the housing during an overmolding process, and the at least one flux concentrator and the at least one hall effect IC are secured within the housing during the overmolding process. 
     According to another embodiment, a method for producing a torque sensor assembly comprising the steps of: (a) disposing at least one flux concentrator and at least one hall effect IC in a cavity of a housing of the torque sensor assembly; and (b) securing a cover to the housing to close the cavity by a laser welding process. 
     According to another embodiment, a method for producing a torque sensor assembly comprising the steps of: (a) disposing at least one flux concentrator and at least one hall effect IC in a cavity of a housing of the torque sensor assembly; and (b) securing a cover to the housing to close the cavity by a laser welding process; wherein step (a) further includes the step of disposing the at least one flux concentrator and the at least one hall effect IC in a carrier to produce a carrier assembly which is then disposed in the cavity of the housing of the torque sensor assembly prior to performing step (b). 
     According to another embodiment, a method for producing a torque sensor assembly comprising the steps of: (a) disposing at least one flux concentrator and at least one hall effect IC disposed in a tooling mold; and (b) forming a housing of the torque sensor assembly in situ in the tooling mold by an overmolding process; wherein the housing includes a cover formed as part of the housing during the overmolding process. 
     Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a first embodiment of a torque sensor assembly in accordance with the present invention. 
         FIG. 2  is a perspective view of the first embodiment of the torque sensor assembly illustrated in  FIG. 1 , the first embodiment of the torque sensor assembly being shown in its assembled state. 
         FIG. 3  is a front view of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 . 
         FIG. 4  is a sectional side view taken along line  4 - 4  of  FIG. 3  of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 . 
         FIG. 5  is an enlarged view of a selected portion of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 , with a carrier of the torque sensor assembly being not shown for clarity. 
         FIG. 6  is another side view of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 . 
         FIG. 7  is a sectional view taken along line  7 - 7  of  FIG. 6  of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 . 
         FIG. 8  is a top view of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 . 
         FIG. 9  is a bottom view of the first embodiment of the torque sensor assembly illustrated in  FIGS. 1 and 2 . 
         FIG. 10  is a perspective view of a second embodiment of a torque sensor assembly in accordance with the present invention, the second embodiment of the torque sensor assembly being shown in its assembled state. 
         FIG. 11  is a front view of the second embodiment of the torque sensor assembly illustrated in  FIG. 10 . 
         FIG. 12  is a sectional side view taken along line  12 - 12  of  FIG. 11  of the second embodiment of the torque sensor assembly illustrated in  FIG. 10 . 
         FIG. 13  is another side view of the second embodiment of the torque sensor assembly illustrated in  FIG. 10 . 
         FIG. 14  is a sectional view taken along line  14 - 14  of  FIG. 13  of the second embodiment of the torque sensor assembly illustrated in  FIG. 10 . 
         FIG. 15  is a bottom view of the second embodiment of the torque sensor assembly illustrated in  FIG. 10 . 
         FIG. 16  is a top view of the second embodiment of the torque sensor assembly illustrated in  FIG. 10  having the overmold portion of the housing removed for clarity. 
         FIG. 17  is another side view of the second embodiment of the torque sensor assembly illustrated in  FIG. 10  which is similar to  FIG. 13  but having the overmold portion of the housing removed for clarity. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIGS. 1-9 , there is illustrated a first embodiment of a torque sensor assembly, indicated generally at  10 , constructed in accordance with the present invention. The torque sensor assembly  10  is preferably adapted to be installed onto a pinion shaft  28  (a portion of which is shown in  FIG. 3 ), which is part of a vehicle steering system (not shown). As best shown in one or both of  FIGS. 1 and 5 , the illustrated torque sensor assembly  10  includes a housing  12 , a carrier  14 , a pair of flux concentrators  16 , a pair of hall effect IC&#39;s (integrated circuits)  18 , a printed circuit board  20 , a cover  22  and a stator  24  disposed on the pinion shaft S. 
     In the illustrated embodiment, the torque sensor assembly  10  can be assembled as follows. First, the stator  24  is disposed on the pinion shaft  28  and then the housing  12  is disposed on the pinion shaft  28  relative to the stator  24 . The flux concentrators  16  and the hall Effect IC&#39;s  18  are disposed in the carrier  14  and the printed circuit  20  is installed on the carrier  14  to produce a carrier assembly. To assist in this, in the illustrated embodiment the carrier  14  is preferably provided with a positioning or locating means or member. In the illustrated embodiment, this is illustrated as being a pair of “upstanding” projections  14 A on the carrier  14  which are disposed or received in a pair openings  20 A provided in the printed circuit board  20 . 
     Next, this carrier assembly is disposed in a cavity or opening  12 A the housing  12 . To assist in this, in the illustrated embodiment the housing  12  is preferably provided with a positioning or locating means or member. In the illustrated embodiment, this is illustrated as being a pair of “upstanding” projections  12 B (only one of which is shown), on the housing  12  which are disposed or received in a pair of openings  14 B provided in the carrier  14 . 
     Following this, in the illustrated embodiment, the cover  22  is installed and secured to the housing  12  by preferably a laser welding process along an outer periphery of the cover  22 . To assist in this, in the illustrated embodiment the housing  12  is preferably provided with a positioning or locating means or member. In the illustrated embodiment, this is illustrated as being a stepped portion or shoulder  12 C on the housing  12  to receive the cover  22  therewithin. To accomplish the laser welding process in the illustrated embodiment, the housing  12  and the cover  22  are preferably formed from suitable like materials, such as for example plastic, which enable the laser welding process to be utilized to secure the housing  12  and the cover  22  together. 
     Alternatively, the housing  12  and/or the cover  22  may be formed from other suitable materials, which may be like and/or non-like materials, which enable the laser welding process to be utilized or any other suitable process or method to be used in order to preferably permanently attach the cover  22  to the housing  12  in a preferably water-tight manner. Examples of such other suitable materials for the cover  22  and/or the housing  12  can include for example, non-metal materials and/or metal materials. Examples of other suitable processes or methods to preferably permanently attach the cover  22  to the housing  12  can include for example, other suitable welding processes selected depending upon the materials for the cover  22  and the housing  12  and/or the use of a suitable adhesive. 
     One advantage of the first embodiment of the torque sensor assembly  10  is that after the carrier assembly has been installed in the housing  12 , the cover  22  is permanently secured to the housing  12  by, in the preferred embodiment, a laser welding process. As a result of this, the chances of water, dirt, debris, or other foreign bodies or contaminants entering past the cover  22  and into the cavity  12 A of the housing  12  is virtually reduced or eliminated since the laser welding process is operative to form a fluid-tight seal between the cavity  12 A of the housing  12  and the cover  22 . Alternatively, the structure or configuration of one or more of the components of the first embodiment of the torque sensor assembly  10  can be other than illustrated and described if so desired. Also, the method for assembling and/or securing the components of the first embodiment of the torque sensor  10  together can be other than illustrated and described if so desired. 
     Referring now to  FIGS. 10-17 , there is illustrated a second embodiment of a torque sensor assembly, indicated generally at  30 , constructed in accordance with the present invention. As best shown in one or more of  FIGS. 10-17 , the illustrated torque sensor assembly  30  includes a housing  32 , a pair of flux concentrators  34 , a pair of hall effect IC&#39;s  36 , a stator  38 , and connector terminals and lead frame  40 . 
     In the illustrated embodiment, the torque sensor assembly  30  can be assembled as follows. First, at least the illustrated components of the torque sensor assembly  30 , which include at least the flux concentrators  34 , the hall effect IC&#39;s  36 , the stator  38  and the connector and lead frame  40  are disposed in a tooling mold  42  (which is schematically shown in  FIG. 16 ). Next, the housing  32  is overmolded in situ to produce the finished or overmolded torque sensor assembly  30  of the second embodiment. To assist in this, in the illustrated embodiment the housing  32  is preferably formed from a suitable material which can be utilized in a suitable molding process, such as for example plastic, which can be utilized in an injection plastic molding process or other suitable molding process. 
     One advantage of the second embodiment of the torque sensor assembly  30  is that the housing  32  is formed as an overmolded housing. As a result of this, water, dirt, debris, or other foreign bodies or contaminants entering through the housing  32  to the components housed therewithin is virtually reduced or eliminated since the overmolding process is operative to enclose the components of the torque sensor assembly  30  which are housed therein in a fluid-tight manner. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.