Patent Publication Number: US-2015083322-A1

Title: Idle Air Control Valve With Plastic Housing And Retention Features

Description:
This application claims the benefit of the earlier filing date of U.S. Provisional Application No. 61/326,757, filed on Apr. 22, 2010, which is hereby incorporated by reference into this specification. 
    
    
     FIELD 
     This invention relates to a linear actuator such as a vehicle idle air control valve (IACV) and, more particularly, to an improved IACV having a plastic housing and retention features. 
     BACKGROUND 
     The IACV is a digital linear actuator (DLA) mounted externally to the intake manifold of automotive engines that accurately controls throttle airflow in an engine system. Axial alignment of the IACV ensures that a pintle/capnut thereof maintains proper alignment with a throttle body or manifold valve seat. The IACV is needed since vehicle pollution emission control regulations require more precise air/fuel ratios and thus cleaner tailpipe emissions. 
     The conventional IACV is an automotive grade can-stack style stepper motor which has been in production for 10-15 years. The conventional IACV has a metal housing for stringent environmental standards requiring that Hexavalent (Cr6) plating replaced by Trivalent (Cr3) plating. This housing met the environmental standards but failed to provide sufficient duration for corrosion protection which may result in a cosmetic annoyance to end customers. 
     Thus, there is a need to provide an improved IACV having a plastic housing that will meet warranty requirements and that can provide a measure of cosmetic appeal due to use of non-corrosive materials. 
     SUMMARY 
     An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is obtained by providing a linear actuator including a plastic housing having an integral flange for mounting the actuator. A stator assembly is disposed in the plastic housing, with the stator assembly having windings. A rotor assembly, having a permanent magnet, is mounted for rotation with respect to the stator assembly such that when the windings are energized, a magnetic field is generated to cause rotation of the rotor assembly. A shaft is restricted from rotation and is associated with the rotor assembly such that rotation of the rotor assembly causes linear movement of the shaft. Connector structure houses leads for powering the windings. The plastic housing has an annular end that captures an annular surface of the connector structure coupling the plastic housing to the connector structure. 
     In accordance with another aspect of the invention, an idle air control valve for a vehicle includes a plastic housing having an integral flange for mounting the actuator. A stator assembly is disposed in the plastic housing with the stator assembly having windings. A rotor assembly, having a permanent magnet, is mounted for rotation with respect to the stator assembly such that when the windings are energized, a magnetic field is generated to cause rotation of the rotor assembly. A shaft is restricted from rotation and is associated with the rotor assembly such that rotation of the rotor assembly causes linear movement of the shaft. A pintle is associated with a distal end of the shaft for linear movement therewith. Connector structure houses leads for powering the windings. The plastic housing has an annular end that captures an annular surface of the connector structure, coupling the plastic housing to the connector structure. 
     In accordance with yet another aspect of the invention, a method provides a plastic housing for an actuator. The actuator has a stator assembly coupled to a connector structure, and a rotor assembly constructed and arranged to rotate with respect to the stator assembly. The method includes inserting the stator assembly with connector structure connected thereto into an interior of the plastic housing until a surface of the stator assembly engages a surface of the plastic housing, with an annular end of the plastic housing extending beyond an adjacent annular surface of the connector structure. The annular end of the housing is then deformed to capture the annular surface of the connector structure, thereby coupling the plastic housing to the connector structure. 
     Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawing, wherein like reference numerals refer to like parts, in which: 
         FIG. 1  is an axial sectional view of an embodiment of a digital linear actuator in the form of an idle air control valve (IACV) in accordance with an embodiment of the invention. 
         FIG. 2  is view of a portion of an end of a plastic housing of the IACV prior to heat forming thereof. 
         FIG. 3  is a view of a portion of the end of the plastic housing of  FIG. 2 , shown after heat rolling to capture a portion of a connector structure. 
         FIG. 4  is a partial sectional view of the end of the plastic housing prior to heat rolling thereof. 
         FIG. 5  is a partial sectional view of the end of the plastic housing after heat rolling and shown capturing a portion of the connection structure. 
         FIG. 6  is a view of the plastic housing of the IACV showing tabs of anti-rotate structure. 
         FIG. 7  is a view showing the anti-rotate structure with a tab engaged in a pocket of the stator assembly of the IACV. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     For illustrative purposes, throughout the following discussion the invention is described as it is incorporated into a particular magnetic device used in a specific product assembly, namely an electric motor, generally indicated at  10 , in the form of a stepper motor that provides linear actuation for an idle air control valve assembly  11  for a vehicle. However, the invention is equally applicable to other linear actuator devices that are employed in harsh environment. 
     With reference to  FIG. 1 , a motor, generalty indicated at  10 , of an Idle Air Control Valve (IACV) for use in a vehicle is shown in accordance with an embodiment of the present invention. The motor  10  includes a plastic housing  12  with integral flange  14  extending outwardly of the housing  12 . A stator assembly, generally indicated at  16 , is disposed in the housing  12 . The stator assembly  16  includes the conventional windings  18 , field cups, pole plates, and bobbins. 
     As shown in  FIG. 1 , a rotor assembly, generally indicated at  20 , is associated with the stator assembly  16 . The rotor assembly  20  has the conventional permanent magnet  22  generally adjacent to the windings  18 . Bearing structure, including a rear, sealed ball bearing  24  and a front eyelet bearing  26  supports the rotor assembly  20  to permit rotation of the rotor assembly  20  relative to the stator assembly  16 . In the embodiment of motor  10  as a stepper motor, introduction of a current in the coil windings  18  of the stator assembly  16  causes rotational movement of the rotor assembly  20 . The rotor assembly  20  has a passage  28  there-through including a threaded portion  30  for engagement with a threaded portion of shaft  32 . The distal end of the shaft  32  is associated with a front bearing  33 , preventing shaft rotation. Therefore, rotational motion of rotor assembly  20  is converted into linear motion of shaft  32 , making this stepper motor a linear actuator. 
     In the embodiment of the motor  10  used in an idle air control valve, the shaft  32  has an integral pintle  34  at its distal end. A spring  36  tends to bias the pintle  34  in an extended position. The pintle  34  receives a cylindrical grime shield  38  to protect against contamination of the motor  10 . With the example of the idle air control valve shown in  FIG. 1 , the motor  10  can be fitted within a bore of an intake manifold or throttle body. To control airflow into the manifold. 
     Since the housing is made of plastic instead of metal, to ensure that the flux path is not disrupted, additional, compensating flux ring structure  40  is provided at the perimeter of the stator assembly  16 . In the embodiments the flux ring structure  40  includes a pair of ferrous material flux rings disposed about the stator assembly  16 , generally adjacent to the windings  18 . 
     The flange  14  provides bolt holes  42  there-through for the mounting hardware to the manifold. Since the material of the flange  14  is plastic (instead of metal), M4 and M5 mounting bolts could damage the plastic flange  14  when torqued to the prescribed installation torque. Thus, metal, preferably split-ring compression limiters  44  are provided in the bolt holes  42  to prevent damage to the flange  14 . The limiters  44  frictionally engage the surfaces defining the bolt holes  42 . 
     An important retention feature of the motor  10  is heat rolling of the plastic housing  12  to capture a connector structure  46  of the motor  10  and thus capture the stator assembly  16  and rotor assembly  20  that are coupled to the connector structure  46 . The connector structure houses leads  47  ( FIG. 4 ) for powering the windings  18  in the conventional manner. Alternative methods of coupling the plastic housing  12  to the connector structure  46  were attempted. For example, molding snap fingers on the inner surface of the housing  12  was not possible. Further, ultrasonic welding of the core of the motor  10  to a plastic housing  12  had mixed results. After thermal cycling, the ultrasonic weld retention load was compromised. Secondary, contamination of the ultrasonic weld surfaces were found unpredictable. Thus, the heat rolling process, explained below, was developed. 
     In accordance with the embodiment and with reference to  FIGS. 2-4 , the connector structure  46  is inserted axially into the interior  49  of the plastic housing  12  until a planar surface  51  of the stator assembly  16  contacts a planar surface  53  ( FIG. 4 ) of the plastic housing  12 . As seen in  FIGS. 2 and 4 , after such insertion, a distal, annular end  48  of the housing  12  extends beyond an annular surface  50  of the connector structure  46 . Thereafter, a heat rolling process heats and deforms the end  48  to capture the annular surface  50  ( FIGS. 1 ,  3  and  5 ) of the connector structure  46  thereby coupling the plastic housing  12  to the connector structure  46 . This heat deformation process of the plastic housing  12  functionally replicates a swaged metal housing. Thus, in the embodiment, the end  48  is deformed to have a radius R of approximately 1.9 mm. 
     The heat roll formation of the plastic is more difficult than the conventional metal swage. Functional requirements for the heat roll connection are, a static  90  N axial load test and also to retain structural integrity after thermal life cycling and thermal vibration. The plastic housing  12  provides sufficient flexure that ensures alignment throughout the range of thermal exposure (e.g., −40 to +125C manifold ambient environment). This flexure, in addition to axial support, provides additional tolerance to manifold vibration since excess vibration can damage the internal motor of the IACV. The heat roll connection between the housing  12  and the connector structure  46  can be air leak tested as witnessed by IACV on the engine manifold. 
     Another important retention feature of the motor  10  is anti-rotate structure created between the plastic housing  12  and the stator assembly  16 . As seen in  FIG. 6 , a plurality of tabs  52 , preferably molded into the hosing  12 , extend in spaced relation about an interior surface  54  of the plastic housing  12 . As shown in  FIG. 7 , the stator assembly  16  includes a plurality of pockets  56 , with one pocket  56  being associated with one tab  52 . Thus, upon assembly of the housing  12  with the stator assembly  16 , each tab  52  engages an associated pocket  56 . The configuration is such that the interference between the pocket  56  and tab  52  is sufficient that the plastic of the tabs  52  and plastic of the surfaces defining the pocket  56  yield or deform creating a tongue and groove anti-rotate interlock structure. The functional requirement for this anti-rotate structure is a 5.5 N-m resistance of the core of the motor turning without violating the angle location requirement of the electrical connector of the connector structure  46 . 
     The plastic used for the housing can by any plastic material suitable for the environment of an idle air control valve. Features of the plastic housing  12  include:
         unique external heat forming the plastic housing end  48  after assembly to retain the core motor   external heat form allows for 360° connector orientation with respect to the housing  12  whereas conventional internal snap retention configurations are location sensitive   heat form method less expensive solution to ultrasonic welding with existing jointing issues   molded internal anti-rotation interlock structure   flange/housing integration eliminates existing jointing issues   flange compression limiters allow use of existing hardware (manifold)   weight savings   the plastic housing exterior eliminates corrosion plating and associated cosmetics rejects   motor efficiency is higher due to provision of the flux ring structure   utilizes existing production core motor with minimal refinements       

     The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.