Abstract:
A throttle body for an automobile includes a housing defining a plurality of bores separated by a central wall. A passageway is defined through the central wall. A shaft is rotatably received within the passageway. A plurality of plates is coupled with the shaft. A contacting preventing means is configured to selectively engage the shaft upon deflection of the shaft in the region of the central wall to prevent contact between the shaft and the housing.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention generally relates to an air intake control device. More specifically, the invention relates to a throttle body in an internal combustion engine having a dual bore throttle body. 
     2. Related Technology 
     Throttle bodies regulate the airflow to an internal combustion engine where the air is mixed with gasoline. Internal combustion engines require a precise mixture of air and gasoline in order to run properly, and therefore throttle bodies are designed to adjustably control the airflow into the cylinders of the engine. In order to control the airflow that reaches the cylinders, the throttle body includes at least one throttle plate (hereinafter “plates”) attached to a throttle shaft and configured such that each throttle plate is located within the throttle bores, or proximal to an end of each of the throttle bores. With rotation of the shaft, the throttle plates are able to selectively obstruct airflow through the throttle bores. More specifically, the throttle plates are able to rotate with respect to each of the bores in order to adjust the cross-sectional area of the bores that is not obstructed by the plates (the “effective area”), thus controlling the airflow that is permitted to flow through the throttle bores. 
     In order to effectively control the effective areas of the bores, the throttle plates are sized and shaped approximately the same as the cross-sections of the bores in order to completely or substantially obstruct the bores when a throttle plate is substantially perpendicular to the airflow (the “closed position”). Additionally, the throttle plates have a minimal thickness in order to not substantially obstruct the throttle bores when the plates are angled such that a throttle plate face is not substantially perpendicular to the airflow (the “open position”). 
     During operation, when the engine is idling, the throttle plates are in the closed position because very little air is needed to mix with the small amount of fuel being injected into the engine. Conversely, the throttle plates are in a variety of open positions at operating speeds higher than idle because more air is needed to mix with the increased amount of fuel being provided to the engine. 
     When the throttle plates are closed, pressure builds on the upstream face of the throttle plate, which is the side of the plate that is closer to the air intake when the throttle plate is closed. If the pressure on the upstream face of the throttle plate is high enough, it may cause the shaft to deflect towards the engine, which can cause unwanted contact between throttle body components, excessive friction between moving parts, and premature part failure. 
     Plural-bore throttle bodies, such as dual-bore throttle bodies, are more susceptible to shaft deflection and premature part failure than single-bore throttle bodies due to length and the positioning of the dual-bore throttle shaft. Dual-bore throttle bodies include two bores and two throttle plates configured side-by-side on a common shaft. Thus, a dual-bore throttle shaft is approximately twice as long as a single-bore throttle shaft. Longer throttle shafts have a greater tendency to deflect than shorter throttle shafts. Additionally, dual-bore throttle bodies include a housing that forms the bores, and the housing typically includes an opening for rotatably receiving the approximate mid-point of the shaft. As with any rigid body, the shaft undergoes maximum deflection near its mid-point. Therefore, dual-bore throttle bodies are particularly susceptible to excessive wear at the point of contact between the throttle shaft mid-point and the housing support opening between the two bores. 
     Therefore, it is desirous to minimize both the throttle shaft deflection and the friction between moving parts. 
     SUMMARY 
     In overcoming the disadvantages and drawbacks of the known technology, the current invention provides an assembly that limits the deflection of the throttle shaft and minimizes the sliding friction between the throttle body&#39;s moving parts. The throttle body includes a housing that defines at least two bores (hereinafter “bores”), which provide airflow to an internal combustion engine. In order to precisely control the airflow into the engine, the bores are coupled with throttle plates rotatably connected to a throttle shaft. The throttle plates are approximately the same size and shape as the bores (and are located inside or near the ends of the bores) such that the airflow through the bores is substantially minimized or completely eliminated when the plates are in a “closed” position. Connected to a rotatable shaft, rotation of the plates controls the amount of airflow through the bores. When the plates are in the closed position, air pressure builds up on one side of the plates and causes the shaft to deflect towards the housing. 
     In order to minimize the friction between the shaft, which may be deflecting and/or rotating, and the housing, a bushing is inserted between the shaft and the midpoint support of the housing. The bushing may be connected to the housing and it may either selectively contact or permanently contact the shaft. More specifically, the shaft and bushing may only selectively contact each other during periods of shaft deflection or permanently contact each other regardless of shaft deflection. Preferably, the shaft and bushing selectively contact each other in order to minimize friction and part wear. 
     The bushing may be of various constructions, such as a ring-shaped bushing, a spring bushing, or a bearing assembly. 
     The ring-shaped bushing may be received in the housing via an opening that is concentric with the shaft. More specifically, the ring-shaped bushing is positioned in a recess in the midpoint support at the housing and the shaft extends through the housing and the ring-shaped bushing. Preferably, the bushing is inserted from one side of the midpoint support and includes a mechanism to limit the depth at which it is inserted into the midpoint support. 
     The spring bushing may be include a slit that permits expansion of the spring bushing diameter. More specifically, as the slit expands, the spring bushing can be snapped over the shaft. Preferably, the spring bushing is received in a reduced diameter portion of the shaft and, in its free state, exhibits an outer diameter that is greater than the outer diameter of the shaft and an inner diameter that is greater than the diameter of the shaft&#39;s reduced diameter portion. 
     The bearing assembly may include a rotating element that contacts the shaft and a support element that positions the rotating element with respect to the shaft. The rotating element may have a circular cross-section to create a smooth and continuous contact between the rotating element and the shaft, and the support element may be enclosed within the housing walls. The height of the rotating element with respect to the shaft may be adjustable. 
     The current invention may also include a plurality of bearings to rotatably receive the shaft. Additionally, a spacer may be coupled with a bearing to form a substantially air-tight seal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-section of a dual-bore throttle body assembly embodying the principles of the present invention; 
         FIG. 2  is a close-up view of a partial cross-section of a second embodiment of the present invention, showing a spring bushing and a throttle shaft; 
         FIG. 3   a  is a front view of the spring bushing shown in  FIG. 2 ; 
         FIG. 3   b  is a side view of the spring bushing shown in  FIG. 3   a ; and 
         FIG. 4  is a partial cross-section of a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a dual-bore throttle body  10 , according to an embodiment of the present invention, used to control the airflow into an internal combustion engine of a motor vehicle. The dual-bore throttle body  10  is in fluid communication with the combustion cylinders of an internal combustion engine (not shown) and configured to control the airflow  28  into the cylinders. The dual-bore throttle body  10  includes a housing  14 , preferably composed of aluminum material, defining a pair of bores  26  and rotatably receiving a shaft  12 . A pair of throttle plates  16  (hereafter “plates”) are fixedly coupled with the shaft  12  such that the throttle plates  16  rotate along with the shaft  12 . During operation, the shaft  12  and throttle plates  16  control the airflow  28  through the bores  26  in order to achieve the optimal mix of air and fuel within the engine. 
     The shaft  12  is coupled with the housing  14  by bearings  22  to allow the shaft  12  to rotate with respect to the housing  14 . The rotation of the shaft  12  is preferably controlled by a control device (not shown), such as a motor and a gear assembly, as will be further discussed below. The shaft  12  is typically composed of steel, brass, or similar materials. 
     As the shaft  12  rotates, the throttle plates  16  likewise rotate and change the angle between the throttle plates  16  and the bores  26 . The plates  16  are positioned and shaped such that the circumference  17  of the throttle plates  16  approximates the inner surface  27  of the bores  26 . More specifically, a plate  16  substantially blocks airflow through a bore  26  when the plate  16  is perpendicular to the bore inner surface  27  (when the plate  16  is in the “closed position”). As the shaft  12  rotates and the plate  16  is no longer in the closed position, the plate  16  no longer substantially prevents airflow through the bore (the plate is in the “open position”). The plates  16  are typically constructed of brass, aluminum, or a similarly suitable material. 
     During operation of the motor vehicle, airflow  28  from the exterior of the vehicle flows through the air induction system, into the bores  26  of the throttle assembly and towards the throttle plate top surface  16   a  . When the throttle plates  16  are in a closed position, as shown in  FIG. 1 , the pressure on the top surface  16   a  of the throttle plates  16  is greater than the resulting pressure on the bottom surface  16   b  . The pressure difference between the top surface  16   a  and the bottom surface  16   b  may cause the shaft  12  to deflect towards the housing lower surface  32 , particularly at the midpoint of the shaft  12 . In order to prevent premature part wear as a result of shaft deflection, a bushing comprised of a low friction material is inserted between the shaft  12  and a central wall  13  (the wall separating the two bores  27 ) of the housing  14 . The low friction material in the bushing may be PTFE, such as Teflon™. 
     In one embodiment, the bushing is a ring-shaped bushing  18  with a substantially circular cross-section. The ring-shaped bushing  18  forms a closed loop, and it is coupled with the housing  14  by sliding the ring-shaped bushing  18  over the shaft  12 . In order to slide the ring-shaped bushing  18  onto the shaft  12  and into position in the central wall  13 , an outer wall  15  of the housing  14  has a first bore  14   a  with a diameter at least as large as an outer diameter  31  of the ring-shaped bushing  18 . The housing also has a second bore  14   b  with a diameter at least as large as the outer diameter of the shaft  12 . The diameter of the second bore  14   b  is preferably smaller than that of the first bore  14   a  in order to minimize air leakage around the shaft  12 . The ring-shaped bushing  18  may have a convex end face to be substantially flush with the bore  27 . The flush connection between the ring-shaped bushing  18  and the bore  27  minimized leakage around the shaft  12  and minimizes turbulent air flow. 
     The first bore  14   a  may be formed by drilling into the outer wall  15  and the central wall  13  along the machine path  20  shown in  FIG. 1 , or by other appropriate methods. The central wall  13  also preferably includes a shoulder  14   c  which separates the first and second bores  14   a ,  14   b  . The shoulder  14   c  is preferably substantially perpendicular to the first and second bores  14   a ,  14   b  in order to form an air-tight seal with the ring-shaped bushing  18 . 
     Formed in this manner, the ring-shaped bushing  18  can be inserted onto the shaft  12  and slid into the first bore  14   a  by press-fitting, or by some other appropriate coupling method. The ring-shaped bushing  18  abuts shoulder  14   c  for lateral support. 
     In order to prevent excessive contact between the shaft  12  and the bushing  18 , the inner diameter of ring-shaped bushing  18  is preferably greater than the diameter of the shaft  12 . A gap  29  is thus located between the shaft  12  and the ring-shaped bushing  18  when the shaft  12  is in the undeflected position seen in  FIG. 1 . The gap  29  reduces contact between the shaft  12  and the ring-shaped bushing  18 , minimizing premature part wear. As the shaft  12  deflects and contacts the ring-shaped bushing  18 , the ring-shaped bushing  18  may or may not rotate along with the shaft  12 , depending on the frictional forces between the shaft  12 , the ring-shaped bushing  18 , and the housing  14 . Preferably, the ring-shaped bushing  18  does not rotate along with the shaft  12 . 
     The dual-bore throttle body  10  is preferably substantially airtight in order to precisely control the airflow  26  into the internal combustion engine. More specifically, the shaft  12 , the bearings  22  and the housing  14  form airtight seals. In order to form the seal  25  at the outer wall  15 , a spacer  24  is inserted between the first bore, the shaft  12  and the bearings  22 . The spacer  24  is preferably plastic, but may be comprised of other suitable materials. 
       FIGS. 2 ,  3   a , and  3   b  show another embodiment of the present invention. In this embodiment, a spring bushing  34  is coupled with the housing&#39;s central wall  13  by a spring force  37  biased towards the central wall  13 . The spring bushing  34  is substantially circular and provided with a slit  36  allowing the spring bushing diameter  50  to be adjustable. More specifically, as a force is applied perpendicularly to the spring bushing outer surface  35 , the spring bushing diameter  50  decreases or increases, depending on the direction of the force. As shown in  FIG. 2 , when the spring bushing  34  is coupled with the central wall  13  of the housing  14 , a housing force  39  is applied to the spring bushing  34  that causes the spring bushing diameter  50  to be smaller than when the spring bushing  34  is in its relaxed state. 
     The shaft  12  in this embodiment preferably includes a reduced diameter section  12   a , wherein the reduced diameter section  12   a  is smaller than the outer diameter of the shaft  12 . When the spring bushing  34  is in a compressed state, the spring bushing diameter  50  is greater than the openings formed by the bearings  22 . Additionally, when the spring bushing  34  is in a relaxed state, the spring pushing diameter  50  is greater than the opening formed by the central wall  13 . Therefore, the spring bushing  34  is preferably installed according to the following steps. First, the shaft  12  is inserted through one of the bearings  22  until the reduced diameter section  12   a  of the shaft  12  is within one of the bores  26 . Secondly, the spring bushing  34  is snapped onto the reduced diameter section  12   a of the shaft  12 . Finally, a radial force is applied to the spring bushing  34  such that the spring bushing diameter  50  is smaller than the opening formed by the central wall  13 , and the spring bushing  34  and shaft  12  are inserted into the opening formed by the central wall  13 . 
     A pair of shoulders  12   b  connect the reduced diameter section  12   a  and the outer diameter of the shaft  12 . During operation, the shoulders  12   b  limit the axial movement of the spring clip bushing  34 . 
     Similarly to the ring-shaped bushing  18 , when the shaft  12  is undeflected, the spring bushing  34  does not contact the shaft  12  because the gap  46 , between the spring bushing  34  and the reduced diameter section  12   a , is smaller than the gap  48  between the central wall  13  and the outer diameter of the shaft  12 . When the shaft  12  is deflected, the spring bushing  34  may or may not rotate along with the shaft  12  during contact between the spring bushing  34  and the rotating, deflected shaft  12 . 
     In order to further minimize shaft  12  wear, the slit  36  is preferably not substantially parallel to the shaft  12 . If the slit  36  is parallel to the shaft  12 , the shaft  12  may contact the spring bushing  34  along the length of the slit  36 , which causes a high pressure area due to the relatively small contact area between the shaft  12  and spring bushing  36 . Therefore, the slit  36  is formed at an angle  52  that is preferably 15° to 45° with respect to the shaft  12 . More preferably, the slit angle  52  is 25° to 35° with respect to the shaft  12 . 
       FIG. 4  shows another embodiment of the present invention, including a bearing assembly  54 . The bearing assembly  54  includes a rotatable element  56  rotatably received by a support element  58 . The rotatable element  56  freely rotates with respect to the support element  58  in order to provide a low friction contact with the shaft  12  via rolling contact. More specifically, the rotatable element  56  rotates along with the shaft  12  when the shaft  12  and the rotatable element  56  contact each other. The rotatable element  56  and the shaft  12  preferably only contact each other during shaft  12  deflection. However, the rolling contact between the shaft  12  and rotatable element  56  causes less friction than the sliding contact between a stationary bushing and the shaft  12 , so the part wear is minimal, even if continuous contact occurs between the shaft  12  and the rotatable element  56 . 
     In order to provide free rotation between the shaft  12  and the rotatable element  56 , the rotatable element  56  has a substantially circular cross section taken along a plane perpendicular to the shaft  12 . More preferably, the rotatable element  56  is spherical-shaped in order to provide static contact regardless of the angle of the contact. 
     The support element  58  is preferably encased within the central wall  13  such that only the rotatable element  56  projects from the central wall  13 . The support element  58  may also include a positioning element  60 , such as a spring or a screw, to adjust the height of the rotatable element  56  with respect to the shaft  12 . However, other appropriate configurations may be used to adjust the height of the rotatable element  56 . 
     The support element  58  includes a receiving end  62  that rotatably receives the rotatable element  56 . Therefore, the shape and size of the receiving end  62  depend on the shape and size of the rotatable element  56 . In  FIG. 4 , the receiving end  62  is cup-shaped to receive the spherical rotatable element  56 . However, other appropriate configurations may be used. 
     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.