Patent Publication Number: US-6666432-B2

Title: Idle speed control valve

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application relates to and incorporates herein by reference Japanese Patent Application No. 2001-40245 filed on Feb. 16, 2001 and Japanese Patent Application No. 2001-345027 filed on Nov. 9, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an idle speed control valve (ISCV) for controlling an air amount supplied to combustion chambers in an internal combustion engine. More particularly, the present invention relates to an idle speed control valve in which an adjusting screw including a stator core is sealed with a sealing material. 
     2. Description of Related Art 
     In general, in an internal combustion engine for a vehicle, a bypass pipe separate from an actual air intake pipe is provided to bypass a throttle valve. An idle speed control valve is provided in the bypass pipe to control an amount of fluid such as air flowing in the bypass pipe. 
     In a general idle speed control valve shown in FIG. 5, an adjusting screw  120  is inserted in a hole  115  provided in a valve body  111  and passes through a center of windings  130 . As shown in FIG. 6, the adjusting screw  120  has a threaded portion  122  on its outer peripheral surface to be threaded with an inner wall of the hole  115 . Adhesive is applied to the threaded portion  122  beforehand, so that the adjusting screw  120  fixes on the inner wall of the hole  115  at a desired position. 
     More specifically, first, an adjusting screw  120  in which the adhesive is not applied is temporary fitted in the hole  115  to adjust a spring for biasing a movable core  141  so that a movement area becomes a predetermined crossing area. Next, adjusting screw  120  is removed from the hole  115  and replaced with adjusting screw  120  with adhesive applied onto the threaded portion  122 . Then, the adjusting screw  120  is finally adjusted and fitted at a predetermined position. Next, a sealing material  150  such as silicon is applied around a head portion  121  of the adjusting screw  120  to improve air-tightness. The sealing material  150  passes between the head portion  121  and the inner wall of the hole  115  and enters the inside of the hole  115 . In this case, since the threaded portion  122  is bonded with the adhesive, the sealing material  150  stops at the threaded portion  122 . (Not shown) 
     Since a replacement of the adjusting screw  120  is required, mounting and assembly time increase and workability is worsened. Thus, if the adjusting screw  120  in which the adhesive is not applied to the threaded portion  122  is used without pre-adjustment and adjusted to the final position, the sealing material  150  applied around the head portion  121  enters deeper inside the control valve  110  beyond the threaded portion  122 . For example, when this sealing material  150  is hardened around a movable core  141 , operation of the movable core  141  is interrupted, and as a result, a valve  145  will not operate. 
     In order to prevent entering of the sealing material  150  around the movable core  141  in the idle speed control valve  110 , a rigid barricade portion may be provided on the outer periphery of the adjusting screw  120 . However, when the barricade portion is press-fitted on the adjusting screw  120  foreign material accumulates and is likely to enter the idle speed control valve  110 . Further, the adjusting screw having the barricade portion requires more torque to be inserted into the hole  115  when compared to that of the adjusting screw  120  without the barricade portion. Therefore, the inner wall defining the hole  115 , and the adjusting screw  120 , are likely to be damaged. 
     Accordingly, in a case where the adhesive is not applied to the threaded portion, the adjusting screw is required to be inserted without damage and also, the sealing material must be restricted from entering the idle speed control valve beyond the threaded portion. 
     SUMMARY OF THE INVENTION 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     According to one embodiment of the present invention, an adjusting screw has a ring-shaped flexible projection on the outer peripheral surface thereof between a threaded portion and a head portion. The flexible projection projects from the outer peripheral surface of the adjusting screw in a radial direction. A width or depth of the flexible projection in a radial direction is substantially equal to a distance between the outer peripheral surface of the adjusting screw and an inner wall of a hole provided in an idle speed control valve body. Therefore, a peak of the flexible projection contacts the inner wall of the hole when the adjusting screw is inserted into the hole. 
     Accordingly, a sealing material, which is applied around a head portion of the adjusting screw for sealing between the outer peripheral surface of the adjusting screw and the inner wall of the hole, is prevented from entering inside of the idle speed control valve beyond the flexible projection. The width of the flexible projection in the radial direction can be greater than the distance between the outer peripheral surface of the adjusting screw and the inner wall. In this case, the peak of the flexible projection is bent backward (opposite to the direction of insertion) when the adjusting screw is inserted into the hole. Therefore, the entering of the sealing material is effectively prevented at the flexible projection. 
     According to another embodiment of the present invention, the adjusting screw has a thin wall portion on which a ring-shaped projection is provided between the threaded portion and the head portion. A width of the projection in the radial direction is greater than a distance between the outer peripheral surface of the thin wall portion and the inner wall of the hole in the idle speed control valve body. Therefore, when the adjusting screw is inserted into the hole, a peak of the projection contacts the inner wall and the thin wall portion having the projection is deformed toward an axial line of the adjusting screw. Accordingly, the sealing material is prevented from entering the inside of the idle speed control valve beyond the projection. Further, a threading torque of the adjusting screw is reduced. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for the purpose of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a cross-sectional view of an idle speed control valve in a longitudinal direction according to a first embodiment of the present invention; 
     FIG. 2 is an enlarged, partial cross-sectional view of an adjusting screw before it is inserted into a hole according to a first embodiment of the present invention; 
     FIG. 3 is an enlarged, partial cross-sectional view of an adjusting screw when it is inserted in a hole according to the first embodiment; 
     FIG. 4A is an enlarged, partial cross-sectional view of an adjusting screw for explaining insertion of the adjusting screw, according to a second embodiment of the present invention; 
     FIG. 4B is an enlarged, partial cross-sectional view of an adjusting screw for explaining insertion of the adjusting screw, according to a second embodiment of the present invention; 
     FIG. 4C is an enlarged, partial cross-sectional view of an adjusting screw for explaining insertion of the adjusting screw, according to a second embodiment of the present invention; 
     FIG. 5 is a related art, cross-sectional view of an idle speed control valve; and 
     FIG. 6 is a related art, enlarged, partial cross-sectional view of an idle speed control valve when it is inserted in a hole. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     First Embodiment 
     Referring to FIG. 1, in an idle speed control valve  10 , a valve body  11  has an inlet passage  19  including an inlet port  18 , an outlet passage  17  including an outlet port  16 , and a cylindrical-shaped hole  15 . Further, the idle speed control valve  10  has an adjusting screw  20  including a stator core  40 , a movable core  41  and a valve  45 . In the valve body  11 , a bobbin  35  and windings  30 , wound around the bobbin  35 , are arranged such that the adjusting screw  20  is inserted in the cylindrical-shaped hole  15  of the valve body  11  and passes through a center of the windings  30 , as shown in FIG.  1 . When the windings  30  are energized, the movable core  41  moves toward the stator core  40 . With this movement, the valve  45  is opened, so that the inlet passage  19  is communicated to the outlet passage  17 . Accordingly, when fluid such as air, that has entered from the inlet port  18  discharges from the outlet port  16 , a discharging amount of the fluid is adjusted with the valve  45 . 
     The adjusting screw  20  is inserted into the cylindrical-shaped hole  15  as shown in FIGS. 2 and 3. A step  13  is provided on the inner wall defining the hole  15  of the valve body  11 , so that an inner diameter of the hole  15  decreases at a left side of the step  13  in FIGS. 2 and 3. The adjusting screw  20  has a head portion  21  and a threaded portion  22 . The adjusting screw  20  is inserted into the hole  15  and tightened on the inner peripheral wall of the hole  15  with the threaded portion  22 . 
     The adjusting screw  20  is, for example, made of rubber and plastic such as polybutylene terephthalate. A ring-shaped flexible projection  26  is provided on the outer peripheral surface of the adjusting screw  20  between the head portion  21  and the threaded portion  22 . The flexible projection  26  projects from the outer peripheral surface of the adjusting screw  20  in a radially outward direction. For example, the flexible projection  26  may be provided such that a rubber ring or plastic ring is fixed by burning or melting the outer peripheral surface of the adjusting screw  20 . Alternatively, the flexible projection  26  may be integrally molded with the adjusting screw  20 . In the latter case, a process forming the projection  26  on the screw  20  is eliminated and overall manufacturing costs may be reduced. Preferably, the flexible projection  26  is triangular-shaped in cross section, as shown in FIG.  2 . When the adjusting screw  20  is inserted into the hole  15 , the flexible projection  26  is pressed against the inner wall defining the hole  15 , and readily bent as shown in FIG.  3 . 
     When the adjusting screw  20  is arranged on the same axial line as that of the cylindrical hole  15 , a width of the projection  26  from the outer peripheral surface of the adjusting screw  20  in the radial direction is equal to or slightly greater than a distance between the inner wall of the hole  15  and the outer peripheral surface of the adjusting screw  20 . That is, the outer diameter of the ring-shaped flexible projection  26  is larger than the inner diameter of the hole  15 . Therefore, when the adjusting screw  20  is inserted into the hole  15 , the peak (outside diameter) of the projection  26  contacts the inner wall of the hole  15  and bends (to right side in FIG. 3) while in contact with the inner wall of the hole  15 . In this way, since the projection  26  is flexibly bent, a torque for inserting the adjusting screw  20  into the hole  15  is reduced as much as possible. Accordingly, it is possible to reduce damage to the inner wall of the hole  15  and the adjusting screw  20  during insertion of the adjusting screw  20 . 
     After the insertion of the adjusting screw  20  with projection  26 , a sealing material  50 , such as silicon, is applied around the head portion  21  of the adjusting screw  20 . The sealing material  50  passes between the adjusting screw  20  and the inner wall of the hole  15  and enters the hole  15 . At this time, the projection  26  functions as a seal, so the sealing material  50  stops at the projection  26 . Thus, the sealing material  50  is prevented from further entering the inside of the hole  15 , that is, beyond the seal  26  or the threaded portion  22 . In this fashion, the operation of the movable core  41  and the valve  45  are not interrupted. In the case that the peak of the projection  26  is bent opposite to the direction of adjusting screw  20  insertion, the sealing material  50  is effectively prevented from further entering the hole  15 . 
     Second Embodiment 
     As shown in FIGS. 4A to  4 C, the adjusting screw  20  has a thin wall portion  29  around the inserting direction. In the second embodiment, a ring-shaped projection  60  is provided on the thin wall portion  29  and between the head portion  21  and the threaded portion  22 . The projection  60  projects from the outer peripheral surface of the thin wall portion  29  in a radially outward direction. Also in the second embodiment, the adjusting screw  20  is, for example, made of rubber and plastic such as polybutylele terephthalate. The projection  60  may be made of a material harder than that of the adjusting screw  20 . A width of the projection  60  in the radial direction is greater than a distance between the outer peripheral surface of the thin wall portion  29  of the adjusting screw  20  and the inner wall defining the hole  15 . That is, the outer diameter of the projection  60  is larger than the inner diameter of the hole  15 , even at the narrowest portion beyond the step  13 . 
     As shown in FIGS. 4A and 4B, when the projection  60  passes the step  13  during the insertion, since the inner diameter of the hole  15  is smaller than the outer diameter of the projection  60  of the adjusting screw  20 , the thin wall portion  29  is deformed toward the axial line of the adjusting screw  20 . At this time, the projection  60  is not generally deformed. Similar to the first embodiment, the threaded portion  22  is then threaded on a threaded portion of the valve body  11  in the hole  15 , so the adjusting screw  20  may be tightened. Then, the sealing material  50 , such as silicon, is applied into the hole  15  as seen in FIG.  4 C. The sealing material  50  passes between the inner wall of the hole  15  and the head portion  21  and enters the hole  15 . Also in this case, since the projection  60  functions as a seal, the sealing material  50  stops at the projection  60 . Since, the sealing material  50  does not enter the inside of the hole  15  beyond the projection  60 , the operation of the movable core  41  and the valve  45  are not interrupted. Further, since the thin wall portion  29  is deformed, a threading torque of the adjusting screw  20  is reduced. Therefore, the adjusting screw  20  is fitted to the valve body  11  without requiring additional torque. Additionally, in the embodiments presented thus far, a resistant force acts on the projections  26  and  60 , and as a result, frictional resistance occurs between the inner wall of the hole  15  and the projections  26  and  60 . This ensures that a torque is required to loosen the adjusting screw  20 . Alternatively, the projections  26  and  60  can be provided on the inner wall of the hole  15 , instead of on the adjusting screw  20 . Further, the projections  26  and  60  may be circular or rectangular in cross section, instead of triangular, for example. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.