Abstract:
A pressure regulator that has a geometry that reduces regulator droop is provided that reduces or eliminates the need for a larger package size for a given set of flow requirements. The regulator comprises a housing having a fuel inlet port and a fuel outlet port; at least one regulation stage having an input in fluidic communication with the fuel inlet port; a final regulation stage comprising an inlet in fluidic communication with an output of the at least one regulation stage, a mating valve seat in fluidic communication with the inlet, and a valve seat in movable contact with the mating valve seat, the valve seat having a bottom having an edge, the edge having means for reducing regulator droop; and means for moving the valve seat from a closed position to an open position in response to a pressure change. The means for reducing regulator droop comprises a reverse lip or an approximately square edge.

Description:
BACKGROUND 
       [0001]    This invention generally relates to fuel systems and, more particularly, to a pressure regulator for a propane fuel system. 
         [0002]    Pressure regulators are used in a large variety of automotive and industrial applications. Within these applications, the pressure regulator delivers a controlled fuel pressure to a downstream metering device, regardless of the fuel tank pressure, fuel flow rate or fuel temperature. In some applications, the regulator is a gaseous media pressure regulator that receives a liquid fuel at the regulator inlet, and vaporizes the fuel prior to the regulator outlet. This function is in addition to the primary function of pressure regulation. 
         [0003]    One industrial application is mobile industrial applications where a pressure regulator is used such as in lift truck applications, more commonly referred to as forklifts. The mobile industrial applications are especially challenging from a fuel system standpoint because they have to be very cost competitive, have to be very compact due to space limitations in the engine compartment, and have high performance expectations based on certified system emissions and drivability requirements. 
         [0004]    Regulator droop is a key performance criterion for gaseous media pressure regulators. Specifically with engine fuel system applications, regulator droop can cause fueling problems at higher engine load and speed conditions due to decreased fuel pressure and/or density delivered to the fuel system mixing device. 
         [0005]    Regulator droop is defined as regulator outlet pressure decreasing with increasing flow media flow rate through the regulator. Sensing area, flow area, spring rate and general flow losses within a regulator are some key parameters that typically affect regulator droop. Changes in these parameters relative to improved droop performance generally involve increasing the size of the features to which these parameters are attributed. Given the typical application requirements of low cost, reduced package size and increased performance, increasing the size of the features contradicts the requirements of low cost and reduced package size. 
       BRIEF SUMMARY 
       [0006]    The high efficiency valve geometry described herein reduces droop through the regulator valve geometry for a given valve opening. Thus, the last parameter mentioned above, flow losses, is improved without increasing cost or part size. Advantages of the geometry, as well as additional inventive features, will be apparent from the description provided herein. 
         [0007]    In one aspect, a lip is added to the bottom of the regulator final regulation stage soft seat that significantly reduces the regulator droop. A gain may also be realized by a similar modification(s) in and around the mating geometry of the final regulator stage hard valve seat. As mentioned above, improved droop performance allows for a smaller package size for a given set of flow requirements. The smaller package size results in an improved regulator package and reduced cost. A sharp square outer edge on the soft seat bottom also gives good performance. 
         [0008]    Other aspects and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0010]      FIG. 1  is a simplified schematic view of an exemplary operating environment in which the regulator may operate; 
           [0011]      FIG. 2  is a partial sectional view of the regulator in a closed position; 
           [0012]      FIG. 3  is a partial sectional view of the regulator in an open position; 
           [0013]      FIG. 4   a  is a graph illustrating the flow performance of the soft seats shown in  FIGS. 4   b  to  4   e;    
           [0014]      FIG. 4   b  is a cross-sectional view of a soft seat of a regulator stage having a reverse lip edge; 
           [0015]      FIG. 4   c  is a cross-sectional view of a soft seat of a regulator stage having a sharp edge; 
           [0016]      FIG. 4   d  is a cross-sectional view of a soft seat of a regulator stage having a radius edge; and 
           [0017]      FIG. 4   e  is a cross-sectional view of a soft seat of a regulator stage having a chamfer edge. 
       
    
    
       [0018]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0019]    Described herein is a pressure regulator that has a valve geometry that reduces regulator droop and that reduces or eliminates the need for a larger package size for a given set of flow requirements. The valve geometry also generally results in lower cost and improved manufacturability. 
         [0020]    Prior to describing the regulator valve geometry, an overview of an exemplary environment in which the regulator can operate shall be described. Referring to  FIG. 1 , an engine system  10  is shown. The engine system  10  comprises an electronic control module (ECM)  12 , a spark-ignited internal-combustion engine  14 , an exhaust system  16 , a spark-producing system  18 , an ignition system  20 , a throttle system  22 , an air intake system  24 , a fuel system  26 , and a trim system  28 . 
         [0021]    The ECM  12  generally monitors, controls, and otherwise manages the operation of the engine system  10  and is operably coupled, via wiring  30  or otherwise, to the above-noted systems  16 - 28 . The ECM  12  typically has full authority over spark, fuel, and air in the engine system  10 . In one embodiment, the ECM  12  is one of the electronic control modules commercially available from Woodward Governor Company of Fort Collins, Colo. If desired, more than one ECM  12  can be utilized by the engine system  10 . 
         [0022]    The engine  10  operates using a vaporized liquid propane gas (LPG), natural gas, or other fuel. The engine  10  is particularly suited for an alternative-fueled off-highway vehicle. The engine  10  includes, among other things, an exhaust port  32 , a spark coupling  34 , an oil pressure switch  36 , a coolant temperature sensor  38 , and an air intake port  40 . 
         [0023]    The exhaust port  32  is generally coupled to the exhaust system  16 . The exhaust system  16  comprises an exhaust pipe  42 , a muffler  44  (including a catalyst), and an oxygen sensor  46 . Note that the catalyst may be a separate component. The exhaust pipe  42  generally extends between the exhaust port  32  and the muffler  44  such that emissions and the by-products of combustion are routed away from the engine  14 . The oxygen sensor  46  is disposed within the exhaust pipe  42  to sense a level of oxygen in the exhaust gases passing through the exhaust pipe, and thus can measure the equivalence ratio. The oxygen sensor  46  is operably coupled to and monitored by the ECM  12 . The muffler  44  is employed to muffle the sound leaving the engine  14  and/or to reduce the level of contaminants in the emissions leaving the engine (i.e., a catalyst function). The muffler  44  is preferably one of a catalytic muffler, a three-way catalyst muffler, and the like. 
         [0024]    The spark coupling  34  is generally coupled to the spark-producing system  18 . In one embodiment, the engine system  10  employs a spark producing system  18  that comprises a distributor  100 , a variable reluctance sensor  102 , and a smart coil  104 . The distributor  100 , variable reluctance sensor  102 , and smart coil  104  operate in conjunction with each other to provide a spark within the engine  14  to combust the fuel found therein. The smart coil  104  is configured to generate a spark. The smart coil  104  has built-in driver circuitry to eliminate the need for a driver circuit inside the ECM  12  or otherwise outside of the smart coil. The smart coil  104  is operably coupled to and monitored by the ECM  12 . Although a smart coil  104  is illustrated in  FIG. 1 , other coil systems can be employed. In some systems, the distributor  100  is eliminated and a plurality of smart coils is used. Either type of spark-producing system  18  may be used with the invention. 
         [0025]    The oil pressure switch  36  monitors the oil pressure within the engine  14 . The coolant temperature sensor  38  monitors the temperature of the coolant flowing in and/or around the engine. Both the oil pressure switch  36  and the coolant temperature sensor  38  are operably coupled to and monitored by the ECM  12 . 
         [0026]    The ignition system  20  comprises a key switch  50 , a power relay  52 , and a fault light  54 . The key switch  50  controls the activation and deactivation of the engine system  10 . Using a key that has been correctly keyed and placed within the key switch  50 , the key switch is moveable to a variety of positions pertaining to the operation of the engine system  10  and engine  14 . For example, the key switch  50  can be switch into an “on” or “run” position, an “accessory” position, and an “off” or “lock” position. 
         [0027]    The power relay  52  is used, for example, to provide power to the ECM when the key switch  50  has been placed in the “on” position. The fault light  54  is an indicator used to warn or alert an operator about conditions related to the engine system  10  such as, for example, that the engine  14  is running or stopped, that the equivalence ratio is undesirable, that one or more components of the engine system  10  are not operating properly or have failed, and the like. Each of the key switch  50 , power relay  52 , and fault light  54  are operably coupled to and monitored by the ECM  12 . 
         [0028]    The air intake port  40  (or plurality of ports) is operably coupled to the air intake system  24 . The air intake system  24  includes an air duct  56 , an air cleaner  58 , a mixer  60 , and a temperature/manifold absolute pressure (TMAP) sensor  62 . The air duct  56 , or air intake manifold, generally extends between the air intake port  40  and the air cleaner  58  such that a source of air is provided to the engine  14 . The air duct  56  is able to carry air from the air cleaner  58 , through the mixer  60 , and to the air intake port  40  of the engine  14 . Various other components (e.g., adapters, etc.) can be included and operably couple together the specifically referenced components. For example, there can be an adapter that plumbs the mixer to the throttle and another adapter the plumbs the throttle to the intake manifold. Other arrangements and mountings of the components are possible without detracting from the spirit of the invention. 
         [0029]    The air cleaner  58  (i.e., air filter) removes contaminants and particles such as, for example, dust, debris, and the like, from the air. The air cleaner  58  is formed from paper, cotton, foam, synthetic materials, and the like. 
         [0030]    The mixer  60  is disposed and/or incorporated into the air duct  56 . The mixer  60  mixes, blends, and/or combines the air and the fuel. In one embodiment, the mixer  60  can be a venturi mixer, a variable venturi mixer, an air-valve mixer, and the like. The mixer  60  includes a reference pressure port  64  and an air valve vacuum port  66  that each pass into the air duct  56  and are exposed to the air therein. The reference pressure port  64  and the air valve vacuum port  66  may be integrally formed with the mixer  60  or mounted separately within the air duct  56  proximate the mixer. In the illustrated embodiment of  FIG. 1 , the reference pressure port  64  is disposed upstream of the mixer  60  (e.g., upstream of an air valve in the mixer) while the air valve vacuum port  66  is disposed downstream of the mixer (e.g., downstream of the air valve in the mixer). As such, the reference pressure port  64  and the air valve vacuum port  66  experience different pressures. 
         [0031]    The TMAP sensor  62  is a sensing device that fits directly into the air duct  56  or is otherwise incorporated into the engine system such as in an intake manifold. As shown in  FIG. 1 , the TMAP sensor  62  is disposed downstream of the mixer  60  and the throttle  70 . The TMAP sensor  62  includes a temperature sensor and a pressure transducer. As such, the TMAP sensor  62  is able to accurately measure temperatures and pressures. In one embodiment, the TMAP sensor  62  senses one or more of the vacuum draw from the engine  14 , a vacuum in the air duct  56 , and/or a barometric pressure depending on whether the key switch  50  is in the “on” position and whether the engine  14  is running or not. For example, the TMAP sensor  62  measures the pressure and temperature of the media proximate the air intake port. If the engine  14  is running and the application is normally aspirated, the pressure the TMAP sensor measures will be below atmospheric pressure. If, on the other hand, the application is turbocharged, the pressure the TMAP sensor  62  measures could be above or below atmospheric pressure depending on the boost level, throttle position, engine speed, and the like. If the engine is not running, the TMAP sensor  62  measures atmospheric pressure. The TMAP sensor  62  is operably coupled to and monitored by the ECM  12 . 
         [0032]    The throttle system  22  includes a foot pedal  68 , a throttle  70 , and a throttle position sensor (TPS)  72 . The foot pedal  68  permits a user of a vehicle to control the position of the throttle  70 . The throttle  70  is disposed within the air duct  56  downstream of the mixer  60  and is, in general, a type of valve used to control the flow of an air/fuel mixture into the engine  14 . In one embodiment, the throttle  70  is a drive-by-wire throttle. Using the foot pedal  68  to control the throttle  70 , the amount of the air/fuel mixture being delivered to the engine  14  is regulated to match the throttle position. As a result, the speed of the vehicle or the work output of the engine can be increased, decreased, or maintained. 
         [0033]    The TPS  72  senses the position of the throttle  70 . In one embodiment, the TPS  72  includes a linear variable resistor that produces a particular linear voltage relative to the position of the throttle  70 . For example, when the engine  14  is at idle, the TPS  72  generates about 0.5 volts and when the throttle  70  is fully open and the engine is running at its maximum the TPS produces about four and a half (4.5)volts. Each of the foot pedal  68 , the throttle  70 , and the TPS  72  are operably coupled to and monitored by the ECM  12 . 
         [0034]    The fuel system  26  is operably coupled to a fuel source (e.g., a fuel tank) and includes a fuel filter  74 , a fuel line  76 , a fuel lock  78 , a regulator  80 , a fuel delivery line  82 , and a coolant line  84 . The fuel filter  74  is a device used to remove contaminants, debris, and/or particles from the fuel supplied by the fuel source. The fuel filter  74  is coupled to the fuel lock  78  by the fuel line  76 . Because the fuel lock  78  is a normally-closed device, when unpowered the fuel lock  78  restricts or prevents the further delivery of fuel and is often vacuum or solenoid actuated. When powered, the fuel lock  78  is a passive device and permits the free flow of fuel. The fuel lock  78  is configured to terminate the supply of fuel to the engine system  10  when an emergency situation arises, when the engine fails, when the key switch  50  is in the “off” position, and the like, and is considered to be a safety device. The fuel lock  78  is operably coupled to and monitored by the ECM  12 . The fuel lock  78  is also operably coupled to the regulator inlet. 
         [0035]    The regulator  80 , which can be a combination of a pressure regulator and vaporizer/heat exchanger, converts a liquid fuel such as, for example, liquid propane to either a gaseous fuel or a mixture of liquid and gaseous fuel and then regulates the pressure of the fuel. In other words, the regulator  80  vaporizes the liquid fuel and regulates the pressure of the fuel. The regulator  80  includes an outlet port  86  and a bias port  88 . The outlet port  86  is operably coupled by the fuel delivery line  82  to the mixer  60 . As such, the vaporized fuel is able to flow from the regulator  80  into the mixer  60 . 
         [0036]    The regulator  80  typically uses the heat generated from the engine  14  to assist in the process of vaporizing the fuel. As shown in  FIG. 1 , the coolant line  84  carries a coolant that has absorbed some of the heat generated by the engine  14 . The heated coolant is flowed inside or proximate the regulator  80  and the heat from the coolant aids in the vaporization of the fuel. It should be noted that the coolant line  84  is not shown connected to anything other than the regulator  80 . It is illustrated this way for clarity and need not be shown in further detail as those skilled in the art will recognize how the coolant line  84  is routed. 
         [0037]    Liquid fuel such as propane enters the regulator  80  and then is vaporized by heat from the engine coolant via coolant line  84  and a pressure drop across a primary pressure regulation stage within the regulator  80 . Heat is transferred to the fuel by the coolant heated passages (heat exchanger) within the regulator  80 . The regulator controls the fuel pressure by metering the fuel flow. The pressure at the bias port  88  alters the pressure of, and therefore the amount of, fuel that flows into the mixer  60 . When engine demand draws fuel from the low-pressure side of the regulator  80 , the regulator opens, letting liquid fuel expand across the primary pressure regulation stage and then flow into the coolant heated chamber, continuing the vaporization process. 
         [0038]    Still referring to  FIG. 1 , the trim system  28  comprises a balance line  90 , a first trim valve  92 , and a second trim valve  94  operably coupled to and operating in conjunction with the mixer  60  and the converter  80 . The balance line  90  is configured to permit the flow of air therethrough and to carry air to and from the air duct  56 . In particular, the balance line  90  permits air to flow from the upstream side of the mixer  60  (e.g., upstream of the air valve in the mixer), through the trim system  28 , then to the downstream side of the mixer (e.g., downstream of the air valve in the mixer). The reference pressure port  64 , the bias port  88 , and the air valve vacuum port  66  are each operably coupled to the balance line  90 . The balance line  90  provides fluid (e.g., air) communication between the reference pressure port  64 , the bias port  88 , and the air vacuum valve port  66 . In one embodiment, the balance line  90  includes an orifice  96  to partially restrict the flow of air. The trim valves  92 ,  94  can also be resized by installing additional orifices (e.g.,  96 ) upstream or downstream of each trim valve. 
         [0039]    The first and second trim valves  92 ,  94  are disposed in the balance line  90  and in fluid communication with the reference pressure port  64 , the bias port  88 , and the air vacuum valve port  66 . The first and second trim valves  92 ,  94 , in conjunction with the orifice  96 , are operable to adjust the pressure at the bias port  88  and thereby control a flow, mass, and/or volume of fuel flowing through the fuel delivery line  82 . As such, the first and second trim valves  92 ,  94  are able to control and/or manage the equivalence ratio (i.e., either phi (φ) or lambda (λ)) of the engine system  10  relative to a control signal from the ECM  12 . 
         [0040]    For example, if the trim valves  92 ,  94  permit too much fuel to flow through the fuel delivery line  82 , the air/fuel ratio becomes too rich. On the other hand, if the trim valves  92 ,  94  permit too little fuel to pass, the air/fuel ratio becomes too be lean. Either of these circumstances results in the engine  14  operating poorly and/or inefficiently. However, if the trim valves  92 ,  94  allow the proper amount of fuel to pass, stoichiometry is achieved (i.e., lambda approaches one) and the engine  14  runs smoothly, efficiently, and with minimal post-catalyst emissions. 
         [0041]    In operation, after the ignition system  20  is used to activate the engine system  10 , air is drawn through the air cleaner  58  and flows through the air duct  56  to the mixer  60 . Simultaneously, fuel (e.g., liquid propane) is introduced into the regulator  80 , vaporized, pressure-regulated and then routed into the mixer  60  via the fuel delivery line  82 . 
         [0042]    Now that the system has been described, the geometry of the regulator shall be described. It should be noted that the regulator may be used in other environments, including those described in U.S. patent application Ser. No. 11/379,458, hereby referenced in its entirety. The description shall be based on a “negative pressure” propane regulator. Regulator “set” pressure is the pressure the regulator attempts to maintain when flowing. The “set” pressure for a “negative pressure” regulator will be below atmospheric pressure. Therefore, the system and/or components connected to the regulator outlet  86  must pull the regulator pressure down to the “set” pressure before the regulator will begin to flow. The function of other regulator types may differ slightly, but the basic principles are the same. 
         [0043]    The pressure regulator  80  functions as follows. Referring additionally to  FIG. 2  and  FIG. 3 , flow media enters the regulator through an inlet port  110 . The flow media may travel through one or more regulation stages  112  prior to the final regulation stage depending on the overall pressure drop across the device and the performance requirements. The regulator may also include a heat exchanger  114 , as is common for propane regulators. A propane regulator receives liquid propane at the regulator inlet  110 . The propane then flashes to vapor due to the pressure drop through the upstream pressure regulation stage(s)  112  and heat provided by the heat exchanger  114 . Next, the flow media enters the inlet  116  of the final regulation stage. 
         [0044]    A given regulation stage can be normally-closed or normally-open, defined by its valve state when it is not pressurized. The final regulation stage of a negative-pressure propane regulator is normally-closed, and thus a soft valve seat  118  is in contact with the mating hard valve seat  120 . This closed state is achieved by a force from the spring  122  pushing up on the lever  124 . The lever  124  pivots around the pivot pin  126  and transfers the spring force to the seat  118 . The mixer  60  or other component immediately downstream of the regulator  80  instigates a vacuum on the outlet of the regulator  80  during the beginning of system operation. This reduction in pressure creates a pressure force on the diaphragm  128  that in turn pushes down on the lever  124 . Once the pressure reaches the “regulation pressure” value, the diaphragm pressure force overcomes the spring force and the valve begins to open. As the valve opens, it allows flow media to flow into the outlet chamber  130 . The regulator  80  will attempt to maintain the regulator “set” pressure, i.e. opening further for higher system flow rates and opening less for lower system flow rates. However, the actual regulated pressure varies due to regulator droop, friction and other factors. 
         [0045]    Regulator droop is defined as regulator outlet pressure decreasing with increasing flow media flow rate through the regulator  80 . Droop is explained as follows. As flow rate through the regulator increases, the regulator valve(s) must open further in an attempt to maintain a constant pressure in the regulator outlet chamber  130 . The force, F, from a spring is a function of its compression, x, and spring rate, k, and is defined in equation form as F=k*x. As the regulation valve opens further due to an increased flow rate, the spring  122  is also compressed further. Given the equation above, and a constant spring rate, the spring force must also increase as the spring deflection increases. This increase in spring force must be countered by an increase of the pressure delta across the diaphragm  128 , and therefore a further reduction in the outlet chamber pressure, i.e. droop, occurs. Flow losses due to increases in flow rate can also contribute significantly to droop. 
         [0046]    Turning now to  FIGS. 4A through 4E , the regulator droop is reduced by changing the features of the edge of the bottom of the soft seat  118 . In one embodiment, a reverse lip  132  is added to the edge of the bottom  140   1 , of the regulator final regulation stage soft seat  118 . The reverse lip  132  significantly reduces the regulator droop, as can be seen in  FIG. 4   a . A gain may also be realized by a similar modification(s) in and around the mating geometry of the hard valve seat  120 . As mentioned above, improved droop performance allows for a smaller package size for a given set of flow requirements. The smaller package size results in an improved regulator package and reduced cost. 
         [0047]    Flow testing results of multiple regulators with “lipped” seats has shown a reduction in part-to-part variation in relation to the regulator pressure vs. flow curves. This is due to the sensitivity of the regulator flow performance to the condition of the bottom outer edge of the soft seat  118 . 
         [0048]    As can be seen in  FIG. 4   a , a sharp square outer edge  134  (see  FIG. 4   c ) on the soft seat bottom  140   2  also gives good performance (although not as good as the “lipped” version). However, the sharp square bottom edge can be difficult to manufacture consistently due to damage that can occur as the part is ejected from the mold. Since the bottom outer edge of the “lipped” version of the seat contains a generous radius, manufacturability is good. A radius  136  on the soft seat bottom  140   3  or a chamfer  138  on the soft seat bottom  140   4  does not provide as good performance as the lip  132  or sharp edge  134 . 
         [0049]    From the foregoing, it can be seen that a regulator having a geometry that reduces regulator droop has been provided. Without the use of the regulator geometry, a larger package size is needed for a given set of flow requirements. 
         [0050]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0051]    Preferred embodiments are described herein, including the best mode known to the inventors. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.