Patent Publication Number: US-8522751-B2

Title: Fuel pressure regulator for a motor vehicle

Description:
BACKGROUND 
     The present invention relates generally to a motor vehicle, and in particular to a fuel pressure regulator for a motor vehicle. 
     Fuel pressure regulators have been previously proposed. Spring based pressure regulators are known that use spring force to control a valve that provides fluid communication to a return fuel line. However, the fuel pressure regulators of the related art do not allow for an efficient method of varying the regulated fuel pressure. There is a need for a design that overcomes these shortcomings of the related art. 
     SUMMARY 
     In one aspect of the invention, a fuel pressure regulation system for a motor vehicle includes a fuel pressure regulator, a spring having a first end portion and a second end portion, a sealing member, an electrical actuating device and an electronic control unit. The fuel pressure regulator includes a first fluid port for receiving pressurized fuel, a second fluid port in fluid communication with a fuel rail and a third fluid port for returning fuel to a fuel tank. The sealing member is mounted to the first end portion of the spring and has a closed position that prevents fluid communication between the first fluid port and the third fluid port. The sealing member has an open position that allows fluid communication between the first fluid port and the third fluid port; the position of the sealing member being determined by the pressure inside the fuel pressure regulator and a length of the spring. The electrical actuating device is configured to adjust the length of the spring and the electronic control unit is configured to send electrical signals to the electrical actuating device to adjust the length of the spring. 
     In another aspect of the invention, a fuel pressure regulation system for a motor vehicle includes a fuel pressure, a fluid filled member capable of deforming and having a set of electrodes, a sealing member, and an electronic control unit. The fuel pressure regulator includes a first fluid port for receiving pressurized fuel, a second fluid port in fluid communication with a fuel rail and a third fluid port for returning fuel to a fuel tank. The fluid filled member is filled with a fluid having an adjustable viscosity. According to one embodiment, the fluid is an electrorheological fluid. According to another embodiment, the fluid is a magnetorheological fluid. The sealing member has a closed position that prevents fluid communication between the first fluid port and the third fluid port and an open position that allows fluid communication between the first fluid port and the third fluid port. The position of the sealing member is determined by the pressure inside the fuel pressure regulator and a viscosity of the adjustable viscosity fluid. The electronic control unit is configured to send electrical signals to the electrodes and the electronic control unit adjusts the regulated fuel pressure by sending electrical signals to the electrodes in order to adjust the viscosity of the fluid of the fluid filled member. 
     In another aspect of the invention, a fuel pressure regulation system for a motor vehicle includes a fuel pressure regulator, and an electronic control unit in communication with the fuel pressure regulator. The electronic control unit adjusts a regulated pressure of the fuel pressure regulator using electrical signals. 
     Other systems, methods, features and advantages of the invention will be, or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a schematic view of an embodiment of a fuel system for a motor vehicle; 
         FIG. 2  is a schematic cross sectional view of an embodiment of a fuel pressure regulator; 
         FIG. 3  is a schematic cross sectional view of an operation of the fuel pressure regulator of  FIG. 2 ; 
         FIG. 4  is a schematic cross sectional view of an operation of the fuel pressure regulator of  FIG. 2 ; 
         FIG. 5  is a schematic cross sectional view of an operation of the fuel pressure regulator of  FIG. 2 ; 
         FIG. 6  is a schematic cross sectional view of an embodiment of a fuel pressure regulator; 
         FIG. 7  is a schematic cross sectional view of an operation of the fuel pressure regulator of  FIG. 6 ; 
         FIG. 8  is a schematic cross sectional view of an operation of the fuel pressure regulator of  FIG. 6 ; and 
         FIG. 9  is a schematic cross sectional view of an operation of the fuel pressure regulator of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view of a fuel system  100  of a motor vehicle. The term “motor vehicle” as used throughout the specification and claims refers to any moving vehicle that is capable of carrying one or more human occupants and is powered by any form of energy. The term “motor vehicle” includes, but is not limited to: cars, trucks, vans, minivans, SUVs, motorcycles, scooters, boats, personal watercraft, and aircraft. In one exemplary embodiment, motor vehicle  100  may be a sports utility vehicle (SUV). 
     In some cases, the motor vehicle includes one or more engines. The term “engine” as used throughout the specification and claims refers to any device or machine that is capable of converting energy. In some cases, potential energy is converted into kinetic energy. For example, energy conversion can include a situation where the chemical potential energy of a fuel or fuel cell is converted into rotational kinetic energy or where electrical potential energy is converted into rotational kinetic energy. Engines can also include provisions for converting kinetic energy into potential energy. For example, some engines include regenerative braking systems where kinetic energy from a drivetrain is converted into potential energy. Engines can also include devices that convert solar or nuclear energy into another form of energy. Some examples of engines include, but are not limited to: internal combustion engines, electric motors, solar energy converters, turbines, nuclear power plants, and hybrid systems that combine two or more different types of energy conversion processes. 
     Generally, the fuel system  100  may be configured to store and deliver fuel to an engine. In some embodiments, the fuel system  100  may deliver fuel to individual fuel injectors of an engine. In an exemplary embodiment, the fuel system  100  may deliver fuel to fuel rails  102  of an engine. The fuel rails  102  may be further associated with fuel injectors  104  that distribute fuel to individual cylinders of an engine. In particular, the fuel injectors  104  may be in fluid communication with the fuel rails  102 . 
     The fuel system  100  includes a fuel tank  103 . The fuel tank  103  may be configured to store a fuel  108  for an engine. In some embodiments, the fuel tank  103  may store a mixed fuel. For example, in some cases, a mixed fuel may be a mixture of gasoline and ethanol. Generally, mixtures of gasoline and ethanol can include different proportions of ethanol including, but not limited to: E20, E75 and E80. In other embodiments, the fuel tank  103  may store a single type of fuel such as gasoline. 
     In some embodiments, the fuel system  100  can be configured with one or more fuel lines for delivering fuel to the fuel rails  102 . In one embodiment, the fuel system  100  can include a fuel line  110 . The fuel line  110  can be any type of tubing or piping that provides fluid communication between the fuel rails  102  and the fuel tank  103 . Furthermore, it will be understood that in different embodiments the fuel line  110  can comprise any number and/or configuration of fuel lines for delivering fuel between the fuel tank  103  and the fuel rails  102 . 
     The fuel system  100  can include provisions for pumping fuel from the fuel tank  103 . In some embodiments, the fuel system  100  may include a fuel pump  120 . For purposes of illustration, the fuel pump  120  is shown in a corner of the fuel tank  103  in the current embodiment. However, in other embodiments, the fuel pump  120  can be disposed in any other location within the fuel tank  103 . In addition, the fuel pump  120  could be optional in some embodiments. For example, in some cases, a gravity feed type system could be used to deliver fuel to an engine. 
     The fuel system  100  can include provisions for regulating the pressure of the fuel  108 . In some embodiments, the fuel system  100  can include a fuel pressure regulator  130 . The fuel pressure regulator  130  may be any device capable of regulating the fuel pressure of the fuel system  100 . In other words, the fuel pressure regulator  130  may be capable of preventing the fuel pressure from rising above a regulated pressure at one or more portions of a fuel line. In an exemplary embodiment, the fuel pressure regulator  130  may be a variable type regulator. Examples of different fuel pressure regulators are discussed in detail below. 
     In different embodiments, the location of the fuel pressure regulator  130  can vary. In some cases, the fuel pressure regulator  130  may be disposed outside of the fuel tank  103 . For example, in some return type fuel systems, the fuel pressure regulator  130  may be disposed adjacent to the fuel rails  102 . In other cases, the fuel pressure regulator  130  may be disposed inside of the fuel tank  103 . In an exemplary embodiment, which uses a returnless type fuel system, the fuel pressure regulator  130  may be disposed within the fuel tank  103 . In particular, in some cases, the fuel pressure regulator  130  may be associated with a portion of the fuel line  110  that is disposed downstream of the fuel pump  120 . With this arrangement, the fuel pressure regulator  130  can help to regulate the pressure of fuel being delivered to the fuel rails  102  from the fuel pump  120 . 
     The fuel system  100  can include provisions for controlling various components. In some embodiments, the fuel system  100  may be associated with a computer or similar device configured to communicate, and in some cases control, the various components associated with the fuel system  100 . In one embodiment, the fuel system  100  can be associated with an electronic control unit  150 , hereby referred to as ECU  150 . 
     The ECU  150  may include a number of ports that facilitate the input and output of information and power. The term “port” as used throughout this detailed description and in the claims refers to any interface or shared boundary between two conductors. In some cases, ports can facilitate the insertion and removal of conductors. Examples of these types of ports include mechanical connectors. In other cases, ports are interfaces that generally do not provide easy insertion or removal. Examples of these types of ports include soldering or electron traces on circuit boards. 
     All of the following ports and provisions associated with the ECU  150  are optional. Some embodiments may include a given port or provision, while others may exclude it. The following description discloses many of the possible ports and provisions that can be used, however, it should be kept in mind that not every port or provision must be used or included in a given embodiment. 
     The ECU  150  can include a port  151  for communicating with the fuel injectors  104 . In some cases, the ECU  150  may be configured to transfer information and/or power to the fuel injectors  104  for injecting fuel into an engine. It will be understood that for purposes of clarity, a single port is used for communicating with the fuel injectors  104 . However, in other embodiments, the ECU  150  could include additional ports for communicating with two or more fuel injectors independently. For example, in another embodiment, the ECU  150  could include eight ports that are configured to connect to each of the eight fuel injectors illustrated in the current embodiment. 
     The ECU  150  can include a port  152  for communicating with the fuel pump  120 . In some cases, the ECU  150  may be configured to transfer information and/or power to the fuel pump  120 . For example, using the port  152 , the ECU  150  may send a control signal to the fuel pump  120  for operating the fuel pump  120  to obtain a desired fuel pressure within the fuel line  110 . 
     The ECU  150  can include a port  153  for communicating with the fuel pressure regulator  130 . In some cases, the ECU  150  may be configured to transfer information and/or power to the fuel pressure regulator  130 . For example, in some cases, the ECU  150  could supply the fuel pressure regulator  130  with a voltage and/or current in order to modify the operation of the fuel pressure regulator  130 . 
     For purposes of clarity, only some components of the fuel system  100  are illustrated in the current embodiment. Other embodiments could include additional components not shown here. For example, in another embodiment, the fuel system  100  could include one or more pressure dampers. Additionally, in some cases, the fuel system  100  could include one or more fuel filters. As another example, some embodiments could include sensors for detecting the operating conditions of the fuel system  100 , including sensors for detecting the pressure inside any of the components of the fuel system  100 . It will also be understood that in embodiments including additional components, the ECU  150  could include additional ports for communicating with these components. 
       FIGS. 2 through 5  illustrate schematic cross sectional views of an embodiment of a fuel pressure regulation system  200  that comprises the fuel pressure regulator  130  and the ECU  150 . Referring to  FIG. 2 , the fuel pressure regulator  130  may include an outer wall  202  that bounds an interior cavity  204 . In some cases, the interior cavity  204  may be divided into a first interior chamber  206  and a second interior chamber  208  by a sealing member  215 . The term “sealing member” as used throughout this detailed description and in the claims refers to any member that may be used to prevent fluid communication between two chambers. It will be understood that any type of sealing member could be used. In some embodiments, various types of valves could be used as a sealing member. Examples of different valves that could be used include, but are not limited to: piston valves, slide valves, globe valves, sleeve valves, ball valves, diaphragm valves, needle valves, check valves, butterfly valves and poppet valves as well as any other type of valves. For purposes of clarity, the sealing member  215  is shown schematically in the current embodiment as a planar member that divides and seals the first interior chamber  206  from the second interior chamber  208 . 
     A fuel pressure regulator can include provisions for allowing the sealing member  215  to move within the interior cavity  204 . In the current embodiment, the sealing member  215  may be mounted directly to a spring  230 . In particular, the sealing member  215  may be mounted to a first end portion  231  of the spring  230 . Therefore, as the spring  230  compresses or extends, the sealing member  215  may translate with the first end portion  231  of the spring  230 . 
     The fuel pressure regulator  130  can include one or more fluid ports. In some embodiments, the fuel pressure regulator  130  may include a first fluid port  210  that provides fluid communication between the second interior chamber  208  and a fuel pump. For example, in the current embodiment, fuel is delivered from the fuel pump  120  through an intake portion  262  of the fuel line  110  and the first fluid port  210  into the second interior chamber  208 . In addition, the fuel pressure regulator  130  may include a second fluid port  212  that provides fluid communication between the second interior chamber  208  and one or more fuel rails. For example, in the current embodiment, fuel exits the second interior chamber  208  through the second fluid port  212  and travels through an outtake portion  264  of the fuel line  110  to the fuel rails  102 . 
     In some embodiments, the fuel pressure regulator  130  may also include a third fluid port  214  that is in fluid communication with a fuel tank. In other words, fuel may also exit the interior cavity  204  at the third fluid port  214  and may be returned directly to the fuel tank. In some situations, this arrangement can help reduce the fuel pressure inside the second interior chamber  208  and downstream of the fuel pressure regulator  130 . 
     Using this arrangement, the sealing member  215  and the spring  230  may comprise a pressure relief valve that helps to limit the pressure within the second interior chamber  208 . In particular, the sealing member  215  may be configured in an open position that provides fluid communication between the third fluid port  214  and the second interior chamber  208 . In other words, when the sealing member  208  is in the open position, fuel entering the first fluid port  210  can exit the second interior chamber  208  through both the second fluid port  212  and the third fluid port  214 . In addition, the sealing member  215  may be configured in a closed position that prevents fluid communication between the third fluid port  214  and the second interior chamber  208 . In other words, when the sealing member  215  is in a closed position, fuel entering through the first fluid port  210  can only exit the second interior chamber  208  through the second fluid port  212 . Moreover, the sealing member  215  may be moved between the open and closed positions according to the pressure within the second chamber  208 . In other words, if the pressure inside the second chamber  208  is high enough to overcome the spring force exerted by the spring  230 , the sealing member  215  may be moved to the open position, which will provide pressure relief and prevent the pressure from rising above the regulated fuel pressure. If, on the other hand, the pressure inside the second chamber  208  is too low to overcome the spring force exerted by the spring  230 , the sealing member  215  may remain in the closed position. 
     A fuel pressure regulator can include provisions for varying the force required to move a sealing member. In embodiments where the position of a sealing member is controlled using a spring, the fuel pressure regulator can include provisions for modifying the spring force. In one embodiment, a fuel pressure regulator can include a manually controlled actuator that compresses the spring and increases the spring force. In an exemplary embodiment, a fuel pressure regulator can include an electrically controlled actuator that compresses the spring using an electrical signal in order to increase the spring force. 
     The fuel pressure regulator  130  can include an electrical actuating device  220 . The term “electrical actuating device” refers to any device capable of producing movement using a received electrical signal. Examples of different electrical actuating devices that can be used include, but are not limited to: electric motors and piezoelectric actuators, as well as other types of electrical actuating devices. In an exemplary embodiment, the electrical actuating device  220  is an electric motor that moves a platform  222 . Moreover, in this case, the electrical actuating device  220  may receive control signals from the ECU  150  by way of the port  153 . In particular, the ECU  150  may apply a voltage or current to electrical actuating device in a manner that controls the movement of the platform  222 . With this arrangement, the movement of the platform  222  can be varied by adjusting the voltage and/or current supplied to the electrical actuating device  220 . 
     In this embodiment, a second end portion  232  of the spring  230  may be mounted to the platform  222 . Therefore, as the platform  222  is moved by the electrical actuating device  220 , the spring  230  may be compressed to various lengths. By varying the compression of the spring  230 , the amount of force required to move the sealing member  215  may also vary. With this arrangement, the regulated pressure of the fuel pressure regulator  130  can be varied by adjusting the compression of the spring  230 , which changes the amount of force required to move the sealing member  215  between the open and closed positions. 
     It will be understood that in some embodiments, the fuel pressure regulator  130  can include provisions for maintaining the sealing member  215  in a fixed position as the spring  230  is compressed. In one embodiment, for example, the fuel pressure regulator  130  can include a stopping ring  290 . In some cases, the stopping ring  290  may be integrally formed with the outer wall  202 . The stopping ring  290  may have a diameter that is substantially smaller than the diameter of the sealing member  215  to prevent the sealing member  215  from moving past the stopping ring  290 . With this arrangement, the position of the first end portion  231  of the spring  230 , which is mounted to the sealing member  215 , may be fixed when the sealing member  215  is in the closed position. Therefore, as the second end portion  232  of the spring  230  is moved, the length of the spring  230  can be adjusted to change the spring force. 
     Referring to  FIGS. 2 and 3 , the operation of the fuel pressure regulator  130  is now discussed. Initially, the ECU  150  controls the electrical actuating device  220  to move the platform  222  to a first position. In this first position, the spring  230  may have length L 1  which is associated with a first spring force. In an exemplary embodiment, the first spring force is selected to prevent the pressure in the second interior chamber  208  from rising above a first regulated pressure. 
     At this time, the fuel pressure within the second interior chamber  208  is not high enough to overcome the first spring force of the spring  230 . Therefore, the sealing member  215  remains in a closed position that prevents fluid communication between the third fluid port  214  and the second interior chamber  208 . As indicated by an intake pressure measurement  242  and an outtake pressure measurement  244 , the pressure at an intake portion  262  of the fluid line  110  is substantially equal to the pressure at an outtake portion  264  of the fluid line  110 . In other words, the pressures of the intake portion  262  and the outtake portion  264  are in substantial equilibrium. 
     As illustrated in  FIG. 3 , as the fuel pressure within the intake portion  262  of the fuel line  110  increases, indicated schematically by an intake pressure measurement  342 , the fuel  108  within the second interior chamber  208  applies a greater force to the sealing member  215 . In this case, the fuel pressure is high enough to overcome the first spring force and compress the spring  230 . In other words, the fuel pressure is above the first regulated fuel pressure. As the spring  230  is compressed, the sealing member  215  moves to an open position in which the third fluid port  214  is in fluid communication with the second interior chamber  208 . This prevents an increase in pressure within the outtake portion  264  of the fuel line  110  (indicated by an outtake pressure measurement  344 ) as fuel exits the second interior chamber  208  through the third fluid port  214  as well as the second fluid port  212 . In other words, the third fluid port  214  provides pressure relief inside the fuel pressure regulator  130  as the sealing member  215  is moved past the third fluid port  214 . This arrangement helps to prevent increases in fuel line pressure that could cause unwanted effects at the fuel injectors  104 . 
     Referring now to  FIGS. 4 and 5 , the regulated fuel pressure of fuel system  100  can be increased by changing the compression of the spring  230  using the electrical actuating device  220 . In this case, the ECU  150  may send a control signal to the electrical actuating device  220  to move the platform  222  to a second position. In this second position, the platform  222  may compress the spring  230  to length L 2 , which is substantially smaller than length L 1  associated with the first position of the platform  222 . By further compressing the spring  230 , the spring force of the spring  230  is increased. In this case, the spring  230  may be associated with a second spring force that is selected to maintain a second regulated pressure that is greater than the first regulated pressure. This second spring force is substantially greater than the first spring force. Therefore, a greater fuel pressure is required to move the sealing member  215  past the third fluid port  214 . 
     As indicated by an intake pressure measurement  442 , the pressure inside the intake portion  262  has been increased. However, the fuel pressure within the second interior chamber  208  is not high enough to overcome the second spring force supplied by the spring  230 . In other words, the fuel pressure is not greater than the second regulated fuel pressure. Therefore, the sealing member  215  remains in the closed position that prevents fluid communication between the third fluid port  214  and the second interior chamber  208 . In this situation, the pressure inside the outtake portion  264  of the fluid line  110  (indicated by an outtake pressure measurement  444 ) remains in equilibrium with the pressure inside the intake fluid portion  262 . 
     As the fuel pressure within the intake portion  262  of the fuel line  110  increases, indicated schematically by an intake pressure measurement  542 , the fuel  108  within the second interior chamber  208  applies a greater force to the sealing member  215 . In this case, the fuel pressure is high enough to overcome the second spring force and compress the spring  230 . In other words, the fuel pressure is greater than the second regulated fuel pressure. As the spring  230  is compressed, the sealing member  215  moves to an open position in which the third fluid port  214  is in fluid communication with the second interior chamber  208 . This prevents an increase in pressure within the outtake portion  264  of the fuel line  110  (indicated by an outtake pressure measurement  544 ) as fuel exits the second interior chamber  208  through the third fluid port  214  as well as the second fluid port  212 . In other words, the third fluid port  214  provides pressure relief inside the fuel pressure regulator  130  as the sealing member  215  is moved past the third fluid port  214 . 
     Using this arrangement, the regulated fuel pressure of the fuel pressure regulator  130  can be varied by controlling the spring force of the spring  230  with the electrical actuating device  220 . Specifically, by applying varying voltages and/or currents, the ECU  150  may control the spring  230  to achieve a desired spring force and thereby obtain a desired regulated fuel pressure. The desired regulated fuel pressure can be selected according to various operating parameters including the current pressure within a fuel pump, the fuel tank pressure, the desired fuel injection amount, as well as any other operating parameters. Furthermore, by using a variable fuel pressure regulator, the fuel pressure regulator can be used directly in the fuel tank of a returnless type fuel system, which provides improved emissions and may eliminate the need for a high performance fuel pump. 
       FIGS. 6 through 9  illustrate schematic cross sectional views of another embodiment of a fuel pressure regulator  530  that may be used with the fuel system  100 . Referring to  FIG. 6 , the fuel pressure regulator  530  may include an outer wall  502  that bounds an interior cavity  504 . In some cases, the interior cavity  504  may be divided into a first interior chamber  506  and a second interior chamber  508  by a sealing member  515 . The term “sealing member” as used throughout this detailed description and in the claims refers to any member that may be used to prevent fluid communication between two chambers. It will be understood that any type of sealing member could be used. In some embodiments, various types of valves could be used as a sealing member. Examples of different valves that could be used include, but are not limited to: piston valves, slide valves, globe valves, sleeve valves, ball valves, diaphragm valves, needle valves, check valves, butterfly valves and poppet valves as well as any other type of valves. For purposes of clarity, sealing member  515  is shown schematically in the current embodiment as a planar member that divides and seals the first interior chamber  506  from the second interior chamber  508 . 
     The fuel pressure regulator  530  can include one or more fluid ports. In some embodiments, the fuel pressure regulator  530  may include a first fluid port  510  that provides fluid communication between the second interior chamber  508  and a fuel pump. For example, in the current embodiment, fuel is delivered from the fuel pump  120  through an intake portion  562  of the fuel line  110  and the first fluid port  510  into the second interior chamber  508 . In addition, the fuel pressure regulator  530  may include a second fluid port  512  that provides fluid communication between the second interior chamber  508  and one or more fuel rails. For example, in the current embodiment, the fuel  108  exits the second interior chamber  508  through the second fluid port  512  and travels through an outtake portion  564  of the fuel line  110  to the fuel rails  102 . 
     In some embodiments, the fuel pressure regulator  530  may also include a third fluid port  514  that is in fluid communication with a fuel tank. In other words, fuel may also exit the interior cavity  504  at the third fluid port  514  and may be returned directly to the fuel tank. In some situations, this arrangement can help reduce the fuel pressure inside the second interior chamber  508  and downstream of the fuel pressure regulator  530 . 
     A fuel pressure regulator can include provisions for allowing the sealing member  515  to move within the interior cavity  504 . In the current embodiment, the sealing member  515  may be mounted directly to a fluid filled member  600 . The fluid filled member  600  may comprise a deformable outer membrane  601  and a fluid  602 . The fluid  602  may be bounded within an interior chamber of the outer membrane  601  so that no fluid can leave the outer membrane. 
     The outer membrane  601  can be comprised of any type of flexible material that is impermeable to some kinds of fluid. Examples of materials that could be used include rubber, plastics as well as any other flexible and impermeable materials. The fluid  602  may comprise any type of fluid. In some embodiments, the fluid  602  may comprise a variable viscosity fluid. In some cases, the fluid  602  could be a smart fluid with a viscosity that changes under an applied electric field or magnetic field. Examples of smart fluids include electrorheological fluids and magnetorheological fluids. In an exemplary embodiment, the fluid  602  may be a magnetorheological fluid. 
     In the current embodiment, a first end portion  631  of the fluid filled member  600  may be mounted to a portion of the outer wall  502 . In addition, a second end portion  632  of the fluid filled member  600  may be mounted to a portion of the sealing member  515 . With this arrangement, as the fluid filled member  600  extends and compresses, the sealing member  515  may translate with the second end portion  632 . 
     The fuel pressure regulator  530  can also include electrodes  610 . The electrodes  610  may be embedded within a portion of the fluid filled member  600 . In particular, the electrodes  610  may be in contact with the fluid  602 . With this arrangement, as a voltage or current is applied to the electrodes  610 , the viscosity of the fluid  602  may be varied. 
     It will be understood that depending on the viscosity of the fluid  602 , the fluid filled member  600  may act as a fluid spring that may provide a restoring force following compression. Moreover, by using a magnetorheological fluid or any type of smart fluid, the viscosity of the fluid  602  can be modified by the application of an electrical signal of some kind. As the viscosity of the fluid  602  is modified, the effective spring force of the fluid filled member  600  can be varied. With this arrangement, the sealing member  515  and the fluid filled member  600  may comprise a pressure relief valve that helps to limit the pressure within the second interior chamber  508 . In particular, the sealing member  515  may be configured in an open position that provides fluid communication between the third fluid port  514  and the second interior chamber  508 . In other words, when the sealing member  515  is in the open position, fuel entering the first fluid port  510  can exit the second interior chamber  508  through both the second fluid port  512  and the third fluid port  514 . In addition, the sealing member  515  may be configured in a closed position that prevents fluid communication between the third fluid port  514  and the second interior chamber  508 . In other words, when the sealing member  515  is in a closed position, fuel entering through the first fluid port  510  can only exit the second interior chamber  508  through the second fluid port  512 . Moreover, the sealing member  515  may be moved between the open and closed positions according to the pressure within the second interior chamber  208 . In other words, if the pressure inside the second interior chamber  208  is high enough to overcome the force exerted by the fluid filled member  600 , the sealing member  515  may be moved to the open position, which will provide pressure relief and prevent the pressure from rising above the regulated fuel pressure. If, on the other hand, the pressure inside the second chamber  508  is too low to overcome the force exerted by the fluid filled member  600 , the sealing member  515  may remain in the closed position. 
     Referring to  FIGS. 6 and 7 , the operation of the fuel pressure regulator  530  is now discussed. Initially, an ECU  550  controls the viscosity of the fluid  602  using an applied voltage and/or current. In the current embodiment, the ECU  550  controls the fluid  602  to have a first viscosity that is associated with a first effective spring force. The term “effective spring force” as used throughout this detailed description and in the claims refers to the restoring force applied by the fluid filled member  600  in order to maintain the fluid filled member  600  in an initial, or equilibrium condition. In an exemplary embodiment, the first viscosity is selected to prevent pressure in the second interior chamber  508  from rising above a first regulated pressure. 
     At this time, the fuel pressure within the second interior chamber  508  is not high enough to overcome the first effective spring force of the fluid  602 . In other words, the fuel pressure is not greater than the first regulated fuel pressure. Therefore, the sealing member  515  remains in a closed position that prevents fluid communication between the third fluid port  514  and the second interior chamber  508 . As indicated by an intake pressure measurement  642  and an outtake pressure measurement  644 , the pressure inside the fluid line  110  before entering the second interior chamber  508  is substantially equal to the pressure inside the fluid line  110  after leaving the fuel pressure regulator  530 . 
     As the fuel pressure within the intake portion  562  of the fuel line  110  increases, indicated schematically by an intake pressure measurement  742 , the fuel  108  within the second interior chamber  508  applies a greater force to the sealing member  515 . In this case, the fuel pressure is high enough to overcome the first effective spring force and compress the fluid filled member  600 . In other words, the fuel pressure is greater than the first regulated fuel pressure. As the fluid filled member  600  is compressed, the sealing member  515  moves to an open position in which the third fluid port  514  is in fluid communication with the second interior chamber  508 . This prevents an increase in pressure within the outtake portion  564  of the fuel line  110  (indicated by an outtake pressure measurement  744 ) as fuel exits the second interior chamber  508  through the third fluid port  514  as well as the second fluid port  512 . In other words, the third fluid port  514  provides pressure relief inside the fuel pressure regulator  530  as the sealing member  515  is moved past the third fluid port  514 . 
     Referring now to  FIGS. 8 and 9 , the regulated fuel pressure of the fuel system  100  can be increased by changing the effective spring force of the fluid  602 . In this case, the ECU  550  may apply a voltage and/or current across the electrodes  610 . Under this applied electric field, the fluid  602  may acquire a second viscosity that is different than the first viscosity. In this case, the second viscosity may be greater than the first viscosity, which may modify the effective spring force of the fluid  602 . In an exemplary embodiment, the fluid  602  may acquire a second effective spring force that is greater than the first effective spring force. Therefore, a greater fuel pressure is required to move the sealing member  515  past the third fluid port  514 . In an exemplary embodiment, the viscosity of the fluid  602  is selected to prevent the pressure from rising above a second regulated pressure that is greater than the first regulated pressure. 
     As indicated by an intake pressure measurement  842 , the pressure inside the intake portion  562  has increased. However, the fuel pressure within the second interior chamber  508  is not high enough to overcome the second effective spring force of the fluid  602 . Therefore, the sealing member  515  remains in a position that prevents fluid communication between the third fluid port  514  and the second interior chamber  508 . In this situation, the pressure inside the outtake portion  564  of the fluid line  110  (indicated by an outtake pressure measurement  844 ) remains in equilibrium with the pressure inside the intake fluid portion  562 . 
     As the fuel pressure within the intake portion  562  of the fuel line  110  increases, indicated schematically by an intake pressure measurement  942 , the fuel  108  within the second interior chamber  508  applies a greater force to the sealing member  515 . In this case, the fuel pressure is high enough to overcome the second effective spring force and compress the fluid filled member  600 . In other words, the fuel pressure is greater than the second regulated fuel pressure. As the fluid filled chamber  600  is compressed, the sealing member  515  moves to a position in which the third fluid port  514  is in fluid communication with the second interior chamber  508 . This prevents an increase in pressure within the outtake portion  564  of the fuel line  110  (indicated by an outtake pressure measurement  944 ) as fuel exits the second interior chamber  508  through the third fluid port  514  as well as the second fluid port  512 . In other words, the third fluid port  514  provides pressure relief inside the fuel pressure regulator  530  as the sealing member  515  is moved past the third fluid port  514 . 
     Using this arrangement, the regulated fuel pressure of the fuel pressure regulator  530  can be varied by controlling the effective spring force of the fluid filled member  600 . Specifically, by applying varying voltages and/or currents, the ECU  550  may control the fluid filled member  600  to achieve a desired effective spring force and thereby obtain a desired regulated fuel pressure. The desired regulated fuel pressure can be selected according to various operating parameters including the current pressure within a fuel pump, the fuel tank pressure, the desired fuel injection amount, as well as any other operating parameters. Furthermore, by using a variable fuel pressure regulator, the fuel pressure regulator can be used directly in the fuel tank of a returnless type fuel system, which provides improved emissions and may eliminate the need for a high performance fuel pump. 
     The arrangement discussed here is not intended to be limited to any type of fuel pressure regulator. In other embodiments, other pressure relief valve arrangements could be used. Additionally, in other embodiments other configurations for fluid ports could be used. Furthermore, the principles discussed here are not limited to any specific mechanism for relieving pressure in a fuel pressure regulator and could be applied to any system where an effective spring constant can be varied through an electrical signal of some kind. 
     While various embodiments of the invention have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.