Abstract:
A fuel control valve assembly that includes a bearing assembly and retainer assembly for a mixture control valve assembly and idle control valve assembly in use with general aviation fuel injector servos is disclosed. The assembly reduces friction and wear on the components of the fuel control valve assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application 62/417,042, filed Apr. 14, 2015, the content of which is incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING GOVERNMENT SUPPORT 
       [0002]    None. 
       FIELD OF THE INVENTION 
       [0003]    The present invention relates to a fuel injection system and valve body assemblies. More specifically, the present invention relates to a fuel injection servo system for an aircraft engine and improved valve assemblies related thereto. 
       BACKGROUND 
       [0004]    Fuel injection systems have replaced carburetors in most modern aircraft engines. Presently, fuel injection systems provide greater performance, economy, and reliability relative to their carburetor counterparts. 
         [0005]    Most prior art fuel injection systems used in aircraft engines are volume-air flow type systems, which are based on the principle of measuring air flow to establish correct fuel flow to the engine cylinders. These systems include a throttle body fuel injection servo which measures the amount of air moving past the throttle by use of a venturi. An in-line diaphragm type flow regulator then converts the air pressure from the venturi into a proportional fuel pressure. During normal operation of the aircraft engine, the position of the throttle controls the air flow through the fuel injection servo or to the regulator, which then controls the flow of fuel to the cylinders. The servo is the primary component used in the fuel injection system and performs all functions required to establish fuel flow volumes. The regulated fuel flow from the servo is sent to a fuel flow divider, which divides the steady stream of fuel into smaller streams of fuel, one for each cylinder. Fuel lines carry fuel from the divider to injector nozzles located in the intake ports of each cylinder. The injectors supply fuel to the intake manifold. Fuel then enters the cylinders from the intake manifold under the low pressure created in the cylinder during the intake cycle. 
         [0006]    During normal operation of the aircraft engine, the position of the throttle and the air flowing through the fuel injection servo or flow regulator controls the flow of fuel to the cylinders of the aircraft engine. As the throttle is opened, more fuel is delivered to each cylinder, resulting in an increase in the speed of the engine or in manifold pressure, and thus more power being generated by the engine. Generally, most fuel injection servos include an air passage mechanism (i.e., the throttle body), a fuel pressure modifying mechanism (i.e., the valve assembly), and a fuel regulator assembly. 
         [0007]      FIG. 1  is a schematic cross-sectional view of a prior art fuel injection system as representative of a Precision Airmotive, LLC brand RSA-5AD1, RSA-5AB1, or RSA-10AD1 system. In the top-left of  FIG. 1 , a valve assembly is shown that includes a mixture control valve and idle control valve. The fuel injection system includes a fuel inlet to accept fuel from, for example, a fuel pump (not shown) before directing such fuel through the fuel strainer and into the cavity housing the mixture control valve and idle control valve. The mixture control valve is connected to the manual mixture control lever. A throttle valve is connected to the idle valve lever. Within the valve assembly cavity housing is also a metering jet for the delivery of fuel, whereby the idle control valve regulates the metered fuel pressure (shown in dark pink) and the mixture control valve regulates the unmetered (inlet) fuel pressure (shown in red), each to separate sides of a fuel diaphragm housed within the fuel regulator of the servo system. 
         [0008]    The valve assembly (i.e., fuel pressure modifying mechanism) receives fuel from a fuel supply and delivers the fuel at a pressure that is different from the fuel supply to the fuel regulator assembly. Some of the major components of valve assembly include an idle valve assembly and a mixture valve assembly. The mixture valve assembly as shown in  FIGS. 1 and 2  includes a mixture valve connected to the mixture control lever. The mixture valve often has a hollow barrel design of cylindrical shape that allows for rotational operation within a bore formed in the valve body. At one end of the mixture control assembly shaft is a roll pin engaged with the shaft adjacent a clip. About the shaft is a spacer, clip and thrust disc, where the flat surfaces are pressed against one by way of a spring that presses against a spring seat. The spring wraps around the exterior of the shaft and variably a portion of the bushing. The bushing may engage the shaft though various seals. The lever is connected to the end of the shaft opposite the clip, spacer and thrust disc, at a point relative to where a second roll pin is positioned. Hole(s) in the non-rotation disc through which fuel can flow, and the hole(s) in the mixture valve shaft can align, permitting the flow of fuel. When misaligned, the fuel is shut off. The discs and hole(s) can also partially permit flow when in intermediate positions. 
         [0009]    The traditional mixture control assembly is shown in  FIGS. 4A-4D , where measurements are relative and may not be drawn to scale. The spring can be seen imparting pressure on the spring seat, and thereon to the thrust disc and clip and/or spacer encircling the shaft. In this example, the spring is noted as 0.854 inches in length down the shaft. 
         [0010]    The idle valve assembly includes an idle valve that is connected to the throttle linkage via an idle valve lever. The idle valve often has a hollow barrel design of cylindrical shape that allows for rotational operation within a bore formed in the valve body. The idle valve generally includes an opening  31  (e.g., a notch cut approximately half way into the side of valve) which communicates with a channel  32  of the regulator assembly for delivering metered fuel to the regulator. At one end of opening is often a stepped slot  31 . The idle valve effectively reduces the area of the main metering jet for accurate metering of the fuel in the engine idle range. 
         [0011]    The idle valve assembly shown in  FIGS. 1 and 3  generally includes an idle valve cover (not shown), a thrust washer/disc (generally, polymer or Teflon), an idle lever spacer, and an o-ring. The idle valve shaft includes a flat disc-like flange  30  having small holes or slots  31  therein. The flat disc-like flange (polymer or Teflon) is held against a second non-rotating flat disc  33  (polymer or Teflon) by a spring (shown in  FIGS. 1 and 2 ) in such a way that the two flat surfaces of the discs are pressed against one another. The hole(s) in the non-rotation disc through which fuel can flow, and the hole(s) in the idle valve shaft can align, permitting the flow of fuel. When misaligned, the fuel is shutting off. The discs and hole(s) can also partially permit flow when in intermediate positions. 
         [0012]    The spring load imposed on the discs creates a load on the shaft tending to push in a direction towards outside of the servo housing. Various efforts have been made to alleviate the friction associated with the discs and other components. For example, polymer thrust washers have been employed for years and are sufficiently durable, but do not reduce friction as is desired. Teflon washers are also utilized, but friction remains. 
         [0013]    The friction and stiffness resulting from the spring-load bearing washer system (“thrust washers”) results in throttle friction. Such stiffness has also led to ‘jumpy’ control settings. Worse, microscopic wear particles thought to be generated from the thrust washers may coalesce with certain constituents (or contamination) in the aviation gasoline found in various regions around the world, particularly the south Asia region. These particles are purported to form particle aggregations that flow downstream, contaminating the fuel system. 
         [0014]    The spring tension and size, coupled with the clip(s) (e.g., c-clip), washers, and other components leave little room for modifications, particularly where such componentry has long been approved by the Federal Aviation Administration. 
         [0015]    A fuel injection system which avoids the shortcomings attendant with the prior art devices and practices utilized heretofore is the subject matter of the present application. The throttle control lever is mechanically linked to a valve which controls fuel to the engine when the throttle is at or very near closed (idle). In various fuel injection servo systems, when the throttle is moved, the idle valve moves. It is often in the idle valve assembly that the high friction affecting throttle movement occurs. 
       SUMMARY OF THE INVENTION 
       [0016]    It should be appreciated that this Summary is provided to introduce a selection of concepts in a simplified form, the concepts being further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of this disclosure, nor is it intended to limit the scope of the invention. 
         [0017]    The present invention dramatically reduces the friction in the throttle and mixture control lever systems, and eliminates the need for polymer or Teflon thrust washers in the fuel injector servo that can be a source of foreign particles that can interact with other materials and contaminate the system. 
         [0018]    In some embodiments, a fuel mixture control assembly is disclosed including a shaft, a stop bracket adapted to be secured on one end of the shaft, a spring arranged over a portion of the shaft, a spring retainer adapted to retain a first end of the spring opposite the stop bracket, a retainer assembly, and a bearing assembly arranged between the spring retainer and the retainer assembly. 
         [0019]    In some embodiments, an idle fuel control assembly is disclosed including a shaft, a bracket adapted to be secured on one end of the shaft, an idle valve member rotationally engaged about the shaft, a retainer assembly, and a bearing assembly arranged adjacent the retainer assembly and the idle valve member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a schematic cross-sectional view of a prior art fuel injection system. 
           [0021]      FIG. 2  is a cross-sectional view of a prior art mixture control assembly. 
           [0022]      FIG. 3  is a cross-sectional view of a prior art idle control assembly. 
           [0023]      FIG. 4A  is a side view of a prior art mixture control assembly. 
           [0024]      FIG. 4B  is a perspective view of a prior art mixture control assembly. 
           [0025]      FIG. 4C  is a cross-sectional view of a prior art mixture control assembly. 
           [0026]      FIG. 4D  is a close-up cross-sectional view of a portion of the prior art mixture control assembly shown in  FIGS. 4A-4C . 
           [0027]      FIG. 5A  is a side view of a mixture control assembly according to one embodiment of the present invention. 
           [0028]      FIG. 5B  is a perspective view of a mixture control assembly according to one embodiment of the present invention. 
           [0029]      FIG. 5C  is a cross-sectional view of a mixture control assembly according to one embodiment of the present invention. 
           [0030]      FIG. 5D  is a close-up cross-sectional view of a portion of the mixture control assembly shown in  FIG. 5C  according to one embodiment of the present invention. 
           [0031]      FIG. 6  is a cross-sectional view of an idle control assembly according to one embodiment of the present invention. 
           [0032]      FIG. 7  is a perspective picture of a mixture control assembly according to one embodiment of the present invention. 
           [0033]      FIG. 8  is a perspective picture of a mixture control assembly according to one embodiment of the present invention. 
           [0034]      FIG. 9  is a close-up perspective picture of a mixture control assembly according to one embodiment of the present invention. 
           [0035]      FIG. 10  is a close-up perspective picture of a mixture control assembly according to one embodiment of the present invention. 
           [0036]      FIG. 11  is a close-up perspective picture of a mixture control assembly according to one embodiment of the present invention. 
           [0037]      FIG. 12  is a close-up perspective picture of a mixture control assembly according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    The present invention will now be described more fully hereinafter with reference to the accompanying figures, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout. In the figures, certain components or features may be exaggerated for clarity, and broken lines may illustrate optional features or elements unless specified otherwise. In addition, the sequence of operations (or steps) is not limited to the order presented in the figures and/or claims unless specifically indicated otherwise. Features described with respect to one figure or embodiment can be associated with another embodiment or figure although not specifically described or shown as such. 
         [0039]    It will be understood that when a feature or element is referred to as being “on” another feature or element, it can be directly on the other feature or element or intervening features and/or elements may also be present. In contrast, when a feature or element is referred to as being “directly on” another feature or element, there are no intervening features or elements present. It will also be understood that, when a feature or element is referred to as being “connected”, “attached” or “coupled” to another feature or element, it can be directly connected, attached or coupled to the other feature or element or intervening features or elements may be present. In contrast, when a feature or element is referred to as being “directly connected”, “directly attached” or “directly coupled” to another feature or element, there are no intervening features or elements present. Although described or shown with respect to one embodiment, the features and elements so described or shown can apply to other embodiments. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items and may be abbreviated as “/”. 
         [0040]    As used herein, phrases such as “between X and Y” and “between about X and Y” should be interpreted to include X and Y. As used herein, phrases such as “between about X and Y” mean “between about X and about Y.” As used herein, phrases such as “from about X to Y” mean “from about X to about Y.” 
         [0041]    Spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. 
         [0042]    It will be understood that although the terms first and second are used herein to describe various features or elements, these features or elements should not be limited by these terms. These terms are only used to distinguish one feature or element from another feature or element. Thus, a first feature or element discussed below could be termed a second feature or element, and similarly, a second feature or element discussed below could be termed a first feature or element without departing from the teachings of the present invention. 
         [0043]    Unless otherwise defined, all terms (including technical and scientific terms) and phrases used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and/or clarity. 
         [0044]    The term “about”, as used herein with respect to a value or number, means that the value or number can vary by +/− twenty percent (20%). The terms “about,” “somewhat,” etc., with respect to structural or functional inter-relations apart from values or numbers are used to convey that an absolute inter-relation is not required, so as the elements satisfy the described purpose within such inter-relation. 
         [0045]    Conventionally, as noted above, the frictional engagement inside the valve assembly of the washers, clips and bushings retained in place by the shaft and spring, impart minimal room for additions or modifications. In some embodiments of the present invention, a ball bearing assembly is included with a shortened spring that is comparably as strong as the prior art springs. 
         [0046]      FIGS. 5A-5D  represent various embodiments of the present invention that reduce friction in the mixture control assembly. In some embodiments shown in  FIG. 5D , the present invention includes a mixture valve assembly  55  including a spring retainer  50 , a ball bearing assembly  61 , a washer retainer  56 , and a washer  57 . Additional common parts to a mixture valve assembly may be included—a bushing  58  (that may be resized to fit the components of the various embodiments herein), a shaft  59 , and a roll pin  60 . 
         [0047]    In some embodiments, the cross-sectional design of the spring retainer  50  has a distinctive cross-sectional design. In some embodiments, the spring retainer  50  is includes a rounded insert  51  sized to extend into at least a portion of the internal circumference of the spring. In some embodiments, the spring retainer  50  includes a shelf  52  on one end of the spring retainer  50  including a circumference sized to accommodate and retain the spring. In some embodiments, the shelf  52  is rounded and of a circumference generally at or near the exterior circumference of the spring  54  (and of greater circumference than the insert  51 ). Opposite the rounded insert  51 , the spring retainer  50  includes a flat surface  53  (extending along the shelf  52 ) for meeting the ball bearing assembly  61 . 
         [0048]    The ball bearing assembly  61  in some embodiments includes a baring cage  63  with one or more balls  62  (e.g., stainless steel) sized to fit within ball-sized spaces in the cage  63 . The ball bearing assembly  61  substantially reduces or eliminates friction in the operation of the mixture control assembly  55 , thereby reducing ‘jumpy’ control settings and/or foreign particle generation. 
         [0049]    In some embodiments, a washer retainer  56 , includes a flat surface  65  for meeting the ball bearing assembly  61  opposite the spring retainer  50 . Opposite the flat surface  65 , the washer retainer  56  includes a seat  66  sized to fit a washer  57  (e.g., C-washer) that may lock into place along the shaft  59  opposite the bushing  58 . The washer retainer  56  may also include a lip  67  to aid in retaining the washer  57 . 
         [0050]    In some embodiments, the bushing(s) may be consistent in size with prior devices. In some embodiments, the bushing may be reduced in size to reduce the amount of change in size required of the spring. The spring  54  may be reduced in size (e.g., from 0.854 inch. to 0.684 inch.), while the strength increased to accommodate the reduction in size.  FIGS. 7-12  show various pictures of the mixture valve assembly  55  of the present invention.  FIG. 11  shows the washer  57  housed in a slot  80  of the shaft  59  for retaining the washer in place. 
         [0051]      FIG. 6  represents various embodiments of the present invention that reduce friction in the idle control assembly  70 . In some embodiments, an idle control bearing assembly  71  may mirror the size and/or shape of the mixture control ball bearing assembly  61 . In some embodiments, an idle control bearing assembly  71  includes an idle bushing  72  may be shaped to include a bushing seat  73  for retaining the idle control bearing assembly  71 . 
         [0052]    The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.