Abstract:
A valve assembly for a fuel pump is disclosed. In certain aspect, the valve assembly includes a housing defining a valve chamber, a valve inlet in fluid communication with the valve chamber, a valve outlet in fluid communication with the valve chamber, a valve seat; a valve body movably disposed within the valve chamber, a retainer sealingly engaging the housing and defining a cavity between the base portion of the valve body and the retainer, wherein the retainer comprises one or more control orifices formed therein and configured to provide fluid communication to the cavity to regulate a position of the valve body based on at least a pressure difference between the valve chamber and the cavity, and a spring member disposed between the retainer and the valve body, wherein the spring member is configured to bias the valve body.

Description:
TECHNICAL FIELD 
       [0001]    This patent disclosure relates generally to high pressure valves and, more particularly, to a system and method for venting high pressure valves. 
       BACKGROUND 
       [0002]    High-pressure fuel pump systems are used in a variety of motorized platforms, including those of trucks, buses, and automobiles, as well as off-road machines utilized in construction, mining, and agricultural fields. They are also utilized in marine as well as industrial applications, the latter including, by way of example, electric power generation and petroleum drilling rigs. Such pumps are generally mechanically driven via associated engines for delivering fuel under high pressure to fuel injectors and into individual cylinders of the engines through so-called common rail fuel systems. 
         [0003]    Common rail fuel systems generally include fuel delivery components associated with a high-pressure variable delivery pumps. A variable delivery pump may be effective to deliver high-pressure fuel into a manifold that acts as a central accumulator for the high-pressure fuel prior to its delivery to individual injectors. The manifold thus dampens pressure fluctuations occurring from discreet high pressure pumping events. Typically, the fuel is sourced from a fuel tank by means of a low pressure fuel transfer pump to the variable delivery high-pressure fuel pump. 
         [0004]    Apart from atmospheric emissions control purposes, the fuel is pressurized to facilitate the accurately timed and controlled delivery of discrete fuel amounts to the fuel injectors. As such, an electronic control system is generally employed to monitor and optimize system fuel pressure. The electronic control system operates the high-pressure pump as well as each of the electronically actuated fuel injectors to optimize fuel pressure and quantity, as well as timing of delivery, under a variety of engine operating conditions. 
         [0005]    Normally, such systems include capabilities for managing fluid dynamics and pressurization of the fuel pump manifold and or rails. As an example, high pressure valves can be used to manage fluid flow and pressure control. However, life of the valve seat is such high pressure valves is often limited due to relative motion and the high contact stress between the valve body and valve seat. The combination of high stress and motion results in adhesive wear which ultimately results in valve leakage. Improvements in valve operation are needed to maintain operable life of the components and minimize leakage. 
         [0006]    As an example, U.S. Pat. No. 5,012,785 (the &#39;785 patent) describes a valve operatively mounted in an axially extending center bore of a high pressure pump rotor. The valve axially shifts between an open position in which a charge of fuel generated by the pump is transmitted as a pressure wave to a fuel injector nozzle and a closed position in which the pump charging chamber is sealed from the injection line and the injection line is vented to low pressure so that secondary pressure waves reflecting from the injector nozzle will be routed to the low pressure line for dissipation therein rather than rebounding from the delivery valve. Although the injection line of the &#39;785 patent is vented, such venting does not address valve motion control and minimizing wear between the valve body and the valve seat. These and other shortcomings of the prior art are address by this disclosure. 
       SUMMARY 
       [0007]    In one aspect, the disclosure describes a housing defining a valve chamber, wherein the valve chamber comprises a first end and a second end opposite the first end; a valve inlet disposed adjacent the first end of the valve chamber and in fluid communication therewith, wherein the valve chamber is configured to receive a flow of fluid from the valve inlet; a valve outlet in fluid communication with the valve chamber to receive a flow of fluid from the valve chamber; a valve seat fixedly disposed at the first end of the valve chamber; a valve body movably disposed within the valve chamber, the valve body comprising a valve head and a base portion; a retainer sealingly engaging the housing and defining a cavity between the base portion of the valve body and the retainer, wherein the retainer comprises one or more control orifices formed therein and configured to provide fluid communication to the cavity to regulate a position of the valve body between the first end and the second end of the valve chamber based on at least a pressure difference between the valve chamber and the cavity; and a spring member disposed between the retainer and the valve body, wherein the spring member is configured to bias the valve body towards the first end of the valve chamber, and wherein the valve head of the valve body is configured to abut against the valve seat to prevent a flow of fluid between the valve inlet and the valve chamber. 
         [0008]    In another aspect, the disclosure describes a housing defining a valve chamber, wherein the valve chamber comprises a first end and a second end opposite the first end; a valve inlet disposed adjacent the first end of the valve chamber and in fluid communication therewith, wherein the valve inlet is in fluid communication with a fuel pump and the valve chamber is configured to receive a flow of fluid from the valve inlet; a valve outlet adjacent the second end of the valve chamber and in fluid communication therewith, wherein the valve outlet is in fluid communication with a fuel manifold and is configured to receive a flow of fluid from the valve chamber and direct the flow of fluid to the manifold; a valve seat fixedly disposed at the first end of the valve chamber; a valve body movably disposed within the valve chamber, the valve body comprising a valve head and a base portion; a retainer sealingly engaging the housing and defining a cavity between the base portion of the valve body and the retainer, wherein the retainer comprises one or more control orifices formed therein and configured to provide fluid communication to the cavity to regulate a position of the valve body between the first end and the second end of the valve chamber based on at least a pressure difference between the valve chamber and the cavity; and a spring member disposed between the retainer and the valve body, wherein the spring member is configured to bias the valve body towards the first end of the valve chamber, and wherein the valve head of the valve body is configured to abut against the valve seat to prevent a flow of fluid between the valve inlet and the valve chamber. 
         [0009]    In yet another aspect, the disclosure describes a housing defining a valve chamber, wherein the valve chamber comprises a first end and a second end opposite the first end; a valve inlet disposed adjacent the first end of the valve chamber and in fluid communication therewith, wherein the valve chamber is configured to receive a flow of fluid from the valve inlet; a valve outlet in fluid communication with the valve chamber to receive a flow of fluid from the valve chamber; a valve seat fixedly disposed at the first end of the valve chamber; a valve body movably disposed within the valve chamber, the valve body comprising a valve head and a base portion, wherein the base portion defines a fluid chamber having a channel formed in an outer surface of the base portion; a retainer sealingly engaging the housing and defining a cavity between the base portion of the valve body and the retainer, wherein the retainer comprises a plurality of control orifices formed therein and configured to provide fluid communication to the cavity to regulate a position of the valve body between the first end and the second end of the valve chamber based on at least a pressure difference between the valve chamber and the cavity, and wherein a position of the valve body between the first end and the second end of the valve chamber controls an alignment of the channel formed in the valve body and one or more of the plurality of control orifices; and a spring member disposed between the retainer and the valve body, wherein the spring member is configured to bias the valve body towards the first end of the valve chamber, and wherein the valve head of the valve body is configured to abut against the valve seat to prevent a flow of fluid between the valve inlet and the valve chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a machine constructed in accordance with the aspects of the disclosure. 
           [0011]      FIG. 2  is a schematic view of a fuel pump manifold and associated fuel rails that may be utilized within a fuel system in accordance with aspects of the disclosure. 
           [0012]      FIG. 3  is a cross-sectional view of a portion of a fuel pump including a valve assembly in accordance with aspects of the present disclosure, where the valve assembly is shown in a closed position. 
           [0013]      FIG. 4  is a cross-sectional view of the valve assembly of  FIG. 3 , showing the valve assembly in an opened position. 
           [0014]      FIG. 5  is a cross-sectional view of a portion of a fuel pump including a valve assembly in accordance with aspects of the present disclosure, where the valve assembly is shown in a closed position. 
           [0015]      FIG. 6  is a cross-sectional view of the valve assembly of  FIG. 5 , showing the valve assembly in an opened position. 
           [0016]      FIG. 7  is a cross-sectional view of a portion of a fuel pump including a valve assembly in accordance with aspects of the present disclosure, where the valve assembly is shown in a closed position. 
           [0017]      FIG. 8  is a cross-sectional view of the valve assembly of  FIG. 7 , showing the valve assembly in an opened position. 
           [0018]      FIG. 9  is a cross-sectional view of the valve assembly of  FIG. 7 , showing the valve assembly in an opened position and venting a cavity to an environment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring now to the drawings, and with specific reference to  FIG. 1 , a machine  10  includes a machine body  12  supported on a conveyance  16 . In the illustrated embodiment, the machine  10  is shown as a mining truck, and the conveyance  16  is shown as wheels. However, the machine  10  could take a wide variety of forms, and the conveyance  16  could also vary substantially. For instance, the conveyance  16  could be tracks or possibly even a propeller in the case of a machine in the form of a seagoing vessel. The machine  10  includes a dump body  14  pivotally attached to the machine body  12 , and also an operator station  15 . One could expect a duty cycle for the machine  10  to include time periods of idling without movement such as when the machine  10  is waiting to receive a load, such as ore, in the dump body  14 , waiting to dump a load, and maybe even waiting to be refueled. Between these motionless idling periods, one might expect the machine  10  to be operating at full power carrying a heaving load in the dump body  14  may be up a steep grade at a mining site. During motionless idling, the engine powering the machine  10  might consume only miniscule amounts of fuel. When operating at full power carrying a heavy load up a steep grade, one might expect the machine  10  to consume relatively large quantities of fuel. 
         [0020]    In certain aspects, the machine  10  may be powered by an engine that includes an intake manifold fluidly connected to a plurality engine cylinders. Referring now to  FIG. 2 , a high-pressure fuel delivery system  30  for such an engine is shown schematically. From the pump manifold  20 , fuel may be directed into respective left and right fuel rails  32  and  34 , by way of respective left and right fuel pump lines or conduits  36  and  38 . The fuel travels into injectors  40  (only one of which is shown) by means of a plurality of injection lines  42 . The injection lines  42  extend from both the left and right rails  32 ,  34 , into each of the injectors  40 . In the described embodiment, it may be appreciated that each of the rails  32 ,  34  supplies fuel to a bank of eight cylinders, thus to a total of 16 cylinders of a V-16 cylinder engine in the disclosed embodiment, and by way of example only. Each of the fuel injectors  40  is adapted to inject pressurized fuel into an associated combustion chamber (not shown) under predetermined conditions of timing, fuel pressure, and fuel flow rate, in accordance with real-time engine conditions, as will be appreciated by those skilled in the art. 
         [0021]    In the described embodiment, the plurality of fuel rails may in some arrangements be replaced by individual canisters or chambers for handling accumulated volumes of fuel prior to actual entry of the fuel into individual injectors. Such chambers or canisters may act as a plurality of fuel injection accumulators, each adapted for supplying pressurized fuel to at least one fuel injector. In such cases, such canisters, chambers, and/or accumulators would be considered equivalent to fuel rails by those skilled in the art, and are so treated herein. 
         [0022]    With respect to the specific embodiment of the fuel rails  32 ,  34  shown and described herein, mounting clamps  44  may be effective to secure the rails within the pump housing  19  of the disclosed embodiment. Alternatively, the structures of the pump manifold  20  and the fuel rails  32 ,  34 , and even the fuel pump conduits  36  and  38  may be formed as an interior part of the housing  19 , or as separate manifold blocks, or even as individual components bolted to the housing  19 .  FIG. 2  also schematically depicts fuel flow from the fuel tank  46  through the low pressure fuel transfer pump  48 , and into the high-pressure pump  18 . As will be discussed in further detail, the high-pressure pump  18  may include or may be in fluid communication with a valve assembly  100  to manage a flow of fluid such as fuel to the manifold. 
         [0023]      FIG. 3  illustrates a cross-sectional view of the valve assembly  100  according to aspects of the present disclosure, where the valve assembly  100  is shown in a closed position. The valve assembly  100  may include a housing  102  having a valve inlet  104  and a valve outlet  106  formed therein. As shown, the valve assembly  100  may include a valve chamber  108  defined by a portion of the housing  102 . The valve chamber  108  may have a first end  110  and a second end  112  opposite the first end  110 . The valve chamber  108  may be in fluid communication with the valve inlet  104  and the valve outlet  106 . As shown in  FIG. 3 , the valve inlet  104  may be disposed adjacent the first end  110  of the valve chamber  108  and the valve outlet  106  may be disposed along a length of the valve chamber  108  between the first end  110  and the second end  112  of the valve chamber  108 . 
         [0024]    The valve body  114  may be moveably disposed in the valve chamber  108 . The valve body  114  may include a valve head  116  formed at a first end  118  of the valve body  114  opposite a second end  120  thereof. As shown, the valve head  116  may be oriented toward the first end  110  of the valve chamber  108 . The valve head  116  may be configured to abut a valve seat  122  formed in a portion of the housing  102 , for example, adjacent the valve inlet  104  at the first end  110  of the valve chamber  108 . As shown in  FIG. 3 , the valve head  116  is in sealing engagement with the valve seat  122  such that the valve assembly  100  is in a closed or seated position. As shown in  FIG. 4 , the valve head  116  is spaced (e.g., lifted) from the valve seat  122  such that the valve assembly  100  is in an opened position. 
         [0025]    Returning to  FIG. 3 , the valve body  114  may include a base portion  117  extending from the valve head  116 . As shown, the base portion  117  may terminate at a first shoulder  126  that extends beyond an outside diameter of the base portion  117 . As an example, a second shoulder  128  may be formed at a portion of the valve head  116  and may extend beyond an outside diameter of the first shoulder  126 . 
         [0026]    A retainer  136  may be disposed adjacent the second end  112  of the valve chamber  108  and may sealingly engage a portion of the housing  102 . A portion of the retainer  136  may define at least a portion of the cavity  134 . As an example, the cavity  134  may be defined by the retainer  136 , a portion of the housing  102 , and the second end  120  of the valve body  114 . 
         [0027]    The retainer  136  may include one or more control orifices  132  extending therethrough. As an example, the control orifices  132  may provide fluid communication between the cavity  134  and a portion of the valve chamber  108 . The control orifices  132  may be of varying size and shape. Further, the control orifices  132  may include one or multiple flow restriction means configured to controllably manipulate flow dynamics of the system. The control orifices  132  may include holes, channels (e.g., flutes), and other arrangement to control flow dynamics through the retainer  136 . 
         [0028]    The retainer  136  may define at least a portion of a fluid chamber  140  such as a low pressure side of the valve assembly  100 . A fluid passage  142  may provide fluid communication between the fluid chamber and a cavity  144  formed between the retainer  136  and the housing  102 . 
         [0029]    A spring member  138  may be disposed in the cavity  134  and may be configured to bias the valve body  114  toward the valve seat  122 . As shown, the spring member  138  is disposed between the retainer  136  and the valve body  114  (e.g., the second shoulder  128 ). As an example, the spring member  138  may be or include a coil spring. Other biasing elements may be used. 
         [0030]    As shown in  FIG. 3 , the valve head  116  is in sealing engagement with the valve seat  122  such that the valve assembly  100  is in a closed or seated position, thereby preventing a flow of the liquid fuel between the valve inlet  104  and the valve chamber  108 . As pressurized fluid flows through the valve inlet  104 , such as during actuation of a plunger or piston of an associated high-pressure pump (e.g., pump  18  ( FIG. 2 )), a force is exerted on the valve head  116  in opposition to the bias of the spring member  138 . As pressure builds at the valve inlet  104 , the forces on the valve head  116  exceed the bias force of the spring member  138  and the valve body  114  moves away from the valve seat  122  and compresses the spring member  138 . As an example, the pressure at the valve inlet  104  may be about 1800-2500 bar during a high pressure operation. Additionally, as the valve body  114  moves away from the valve seat  122 , the fluid in the cavity  134  is compressed, thereby providing an additional biasing force in opposition of the movement of the valve body  114  toward the cavity  134 . The fluid pressure in the cavity  134  mitigates pressure impulses that would normally cause the valve body  114  to compress the spring member  138  and even contact the retainer  136  at high velocities. The dimensions of the control orifices  132 , a cross-sectional area of the valve body  114 , and the stiffness of the spring member  138  may be configured so as to control a movement and/or position of the valve body  114  under various pressure conditions. 
         [0031]    As shown in  FIG. 4 , the valve head  116  is spaced (e.g., lifted) from the valve seat  122  such that the valve assembly  100  is in an opened position. As such, fluid may flow from the valve inlet  104  to the valve outlet  106  and on to a manifold such as a manifold  20  ( FIG. 2 ), for example. When pressure is reduced at the valve inlet  104 , the spring member  138  biases the valve body  114  toward the valve seat  122 . However, the bias force of the spring member  138  is controlled by a pressure change in the cavity  134 . For example, as the valve body  114  moves toward the valve seat  122 , a pressure is reduced in the cavity  134  causing an opposing force to the bias of the spring member  138 . The control orifices  132  allow fluid to back fill the cavity  134  is a controlled manner and such control orifices  132  may be configured along with the spring member  138  to provide a controlled motion of the valve body  114 . 
         [0032]    As an illustrative example, as the linear motion of the valve body  114  changes the volume of the cavity  134 , a sudden motion of the valve body  114  is impeded by the flow dynamics of the cavity  134 . Therefore, the cavity  134  decreases the maximum impact velocity of both the strokes and return motions of the valve body  114 . As such, wear of the valve assembly  100  may be reduced and the life expectancy of the spring member  138  may be increased. 
         [0033]      FIG. 5  illustrates a cross-sectional view of the valve assembly  200  according to aspects of the present disclosure, where the valve assembly  200  is shown in a closed position. The valve assembly  200  may include a housing  202  having a valve inlet  204  and a valve outlet  206  formed therein. As shown, the valve assembly  200  may include a valve chamber  208  defined by a portion of the housing  202 . The valve chamber  208  may have a first end  210  and a second end  212  opposite the first end  210 . The valve chamber  208  may be in fluid communication with the valve inlet  204  and the valve outlet  206 . As shown in  FIG. 5 , the valve inlet  204  may be disposed adjacent the first end  210  of the valve chamber  208  and the valve outlet  206  may be disposed along a length of the valve chamber  208  between the first end  210  and the second end  212  of the valve chamber  208 . 
         [0034]    The valve body  214  may be moveably disposed in the valve chamber  208 . The valve body  214  may include a valve head  216  formed at a first end  218  of the valve body  214  opposite a second end  220  thereof. As shown, the valve head  216  may be oriented toward the first end  210  of the valve chamber  208 . The valve head  216  may be configured to abut a valve seat  222  formed in a portion of the housing  202 , for example, adjacent the valve inlet  204  at the first end  210  of the valve chamber  208 . As shown in  FIG. 5 , the valve head  216  is in sealing engagement with the valve seat  222  such that the valve assembly  200  is in a closed or seated position. As shown in  FIG. 6 , the valve head  216  is spaced (e.g., lifted) from the valve seat  222  such that the valve assembly  200  is in an opened position. 
         [0035]    Returning to  FIG. 7 , the valve body  214  may include a base portion  217  extending from the valve head  216 . As shown, the base portion  217  may terminate at a first shoulder  226  that extends beyond an outside diameter of the base portion  217 . As an example, a second shoulder  228  may be formed at a portion of the valve head  216  and may extend beyond an outside diameter of the first shoulder  226 . 
         [0036]    A retainer  236  may be disposed adjacent the second end  212  of the valve chamber  208  and may sealingly engage a portion of the housing  202 . A portion of the retainer  236  may define at least a portion of the cavity  234 . As an example, the cavity  234  may be defined by the retainer  236 , a portion of the housing  202 , and the second end  220  of the valve body  214 . 
         [0037]    The retainer  236  may include one or more control orifices  232  extending therethrough. As an example, the control orifices  232  may provide fluid communication between the cavity  234  and a fluid chamber  240  such as a low pressure side of the valve assembly  200 . As a further example, the fluid chamber  240  may experience pressures on the order of about 4-5 bar. The control orifices  232  may be of varying size and shape. Further, the control orifices  232  may include one or multiple flow restriction means configured to controllably manipulate flow dynamics of the system. The control orifices  232  may include holes, channels (e.g., flutes), and other arrangement to control flow dynamics through the retainer  236 . 
         [0038]    The retainer  236  may define at least a portion of the fluid chamber  240  such as a low pressure side of the valve assembly  200 . As a further example, the fluid chamber  240  may experience pressures on the order of about 4-5 bar. A fluid passage  242  may provide fluid communication between the fluid chamber and a cavity  244  formed between the retainer  236  and the housing  202 . 
         [0039]    A spring member  238  may be disposed in the cavity  234  and may be configured to bias the valve body  214  toward the valve seat  222 . As shown, the spring member  238  is disposed between the retainer  236  and the valve body  214  (e.g., the second shoulder  228 ). As an example, the spring member  238  may be or include a coil spring. Other biasing elements may be used. 
         [0040]    As shown in  FIG. 5 , the valve head  216  is in sealing engagement with the valve seat  222  such that the valve assembly  200  is in a closed or seated position, thereby preventing a flow of the liquid fuel between the valve inlet  204  and the valve chamber  208 . As pressurized fluid flows through the valve inlet  204 , such as during actuation of a plunger or piston of an associated high-pressure pump (e.g., pump  18  ( FIG. 2 )), a force is exerted on the valve head  216  in opposition to the bias of the spring member  238 . As pressure builds at the valve inlet  204 , the forces on the valve head  216  exceed the bias force of the spring member  238  and the valve body  214  moves away from the valve seat  222  and compresses the spring member  238 . As an example, the pressure at the valve inlet  204  may be about 1800-2500 bar during a high pressure operation. Additionally, as the valve body  214  moves away from the valve seat  222 , the fluid in the cavity  234  is compressed, thereby providing an additional biasing force in opposition of the movement of the valve body  214  toward the cavity  234 . The fluid pressure in the cavity  234  mitigates pressure impulses that would normally cause the valve body  214  to compress the spring member  238  and even contact the retainer  236  at high velocities. The dimensions of the control orifices  232 , a cross-sectional area of the valve body  214 , and the stiffness of the spring member  238  may be configured so as to control a movement and/or position of the valve body  214  under various pressure conditions. 
         [0041]    As shown in  FIG. 6 , the valve head  216  is spaced (e.g., lifted) from the valve seat  222  such that the valve assembly  200  is in an opened position. As such, fluid may flow from the valve inlet  204  to the valve outlet  206  and on to a manifold such as manifold  20  ( FIG. 2 ), for example. When pressure is reduced at the valve inlet  204 , the spring member  238  biases the valve body  214  toward the valve seat  222 . However, the bias force of the spring member  238  is controlled by a pressure change in the cavity  234 . For example, as the valve body  214  moves toward the valve seat  222 , a pressure is reduced in the cavity  234  causing an opposing force to the bias of the spring member  238 . The control orifices  232  allow fluid to back fill the cavity  234  is a controlled manner and such control orifices  232  may be configured along with the spring member  238  to provide a controlled motion of the valve body  214 . 
         [0042]    As an illustrative example, as the linear motion of the valve body  214  changes the volume of the cavity  234 , a sudden motion of the valve body  214  is impeded by the flow dynamics of the cavity  234 . Therefore, the cavity  234  decreases the maximum impact velocity of both the strokes and return motions of the valve body  214 . As such, wear of the valve assembly  200  may be reduced and the life expectancy of the spring member  238  may be increased. 
         [0043]      FIG. 7  illustrates a cross-sectional view of the valve assembly  300  according to aspects of the present disclosure, where the valve assembly  300  is shown in a closed position. The valve assembly  300  may include a housing  302  having a valve inlet  304  and a valve outlet  306  formed therein. As shown, the valve assembly  300  may include a valve chamber  308  defined by a portion of the housing  302 . The valve chamber  308  may have a first end  310  and a second end  312  opposite the first end  310 . The valve chamber  308  may be in fluid communication with the valve inlet  304  and the valve outlet  306 . As shown in  FIG. 7 , the valve inlet  304  may be disposed adjacent the first end  310  of the valve chamber  308  and the valve outlet  306  may be disposed along a length of the valve chamber  308  between the first end  310  and the second end  312  of the valve chamber  308 . 
         [0044]    The valve body  314  may be moveably disposed in the valve chamber  308 . The valve body  314  may include a valve head  316  formed at a first end  318  of the valve body  314  opposite a second end  320  thereof. As shown, the valve head  316  may be oriented toward the first end  310  of the valve chamber  308 . The valve head  316  may be configured to abut a valve seat  322  formed in a portion of the housing  302 , for example, adjacent the valve inlet  304  at the first end  310  of the valve chamber  308 . As shown in  FIG. 7 , the valve head  316  is in sealing engagement with the valve seat  322  such that the valve assembly  300  is in a closed or seated position. As shown in  FIGS. 8 and 9 , the valve head  316  is spaced (e.g., lifted) from the valve seat  322  such that the valve assembly  300  is in an opened position. 
         [0045]    Returning to  FIG. 7 , the valve body  314  may include a base portion  317  extending from the valve head  316 . As shown, the base portion  317  may terminate at a first shoulder  326  that extends beyond an outside diameter of the base portion  317 . As an example, a second shoulder  328  may be formed at a portion of the valve head  316  and may extend beyond an outside diameter of the first shoulder  326 . 
         [0046]    A retainer  336  may be disposed adjacent the second end  312  of the valve chamber  308  and may sealingly engage a portion of the housing  302 . A portion of the retainer  336  may define at least a portion of the cavity  334 . As an example, the cavity  334  may be defined by the retainer  336 , a portion of the housing  302 , and the second end  320  of the valve body  314 . The retainer  336  may also define at least a portion of the fluid chamber  340  such as a low pressure side of the valve assembly  300 . As a further example, the fluid chamber  340  may experience pressures on the order of about 4-5 bar. 
         [0047]    The retainer  336  may include one or more control orifices  330 ,  332  extending therethrough. As an example, a first control orifice  330  may provide fluid communication between the valve chamber  308  and the cavity  334 . As another example, a second control orifice  332  may provide fluid communication between the cavity  334  and an environment external to the valve assembly  300 . The control orifices  330 ,  332  may be of varying size and shape. Further, the control orifices  330 ,  332  may include one or multiple flow restriction means configured to controllably manipulate flow dynamics of the system. The control orifices  330 ,  332  may include holes, channels (e.g., flutes), and other arrangement to control flow dynamics through the retainer  336 . 
         [0048]    As shown in  FIG. 7 , a fluid chamber  331  may be formed in the valve body  314  and may terminate in fluid communication with the cavity  334 . A channel  333  may be formed about at least a portion of the periphery of the valve body  314  and may be in fluid communication with the fluid chamber  331 . As the valve body  314  moves from the first end  310  of the valve chamber  308  toward the second end  312  of the valve chamber  308  the channel  333  may align with the first control orifice  330  and/or the second control orifice  332  to provide fluid communication with the cavity  334 . 
         [0049]    A spring member  338  may be disposed in the cavity  334  and may be configured to bias the valve body  314  toward the valve seat  322 . As shown, the spring member  338  is disposed between the retainer  336  and the valve body  314  (e.g., the second shoulder  328 ). As an example, the spring member  338  may be or include a coil spring. Other biasing elements may be used. 
         [0050]    As shown in  FIG. 7 , the valve head  316  is in sealing engagement with the valve seat  322  such that the valve assembly  300  is in a closed or seated position, thereby preventing a flow of the liquid fuel between the valve inlet  304  and the valve chamber  308 . As pressurized fluid flows through the valve inlet  304 , such as during actuation of a plunger or piston of an associated high-pressure pump (e.g., pump  18  ( FIG. 2 )), a force is exerted on the valve head  316  in opposition to the bias of the spring member  338 . As pressure builds at the valve inlet  304 , the forces on the valve head  316  exceed the bias force of the spring member  338  and the valve body  314  moves away from the valve seat  322  and compresses the spring member  338 . As an example, the pressure at the valve inlet  304  may be about 1800-2500 bar during a high pressure operation. Additionally, as the valve body  314  moves away from the valve seat  322 , the fluid in the cavity  334  is compressed, thereby providing an additional biasing force in opposition of the movement of the valve body  314  toward the cavity  334 . The fluid pressure in the cavity  334  mitigates pressure impulses that would normally cause the valve body  314  to compress the spring member  338  and even contact the retainer  336  at high velocities. The dimensions of the control orifices  332 , a cross-sectional area of the valve body  314 , and the stiffness of the spring member  338  may be configured so as to control a movement and/or position of the valve body  314  under various pressure conditions. 
         [0051]    As shown in  FIG. 8 , the valve head  316  is spaced (e.g., lifted) from the valve seat  322  such that the valve assembly  300  is in an opened position. As such, fluid may flow from the valve inlet  304  to the valve outlet  306  and on to a manifold such as manifold  20  ( FIG. 2 ), for example. When pressure is reduced at the valve inlet  304 , the spring member  338  biases the valve body  314  toward the valve seat  322 . However, the bias force of the spring member  338  is controlled by a pressure change in the cavity  334 . For example, as the valve body  314  moves toward the valve seat  322 , a pressure is reduced in the cavity  334  causing an opposing force to the bias of the spring member  338 . In certain aspects, the first control orifice  330  facilitates fluid communication between the valve chamber  308  and the cavity  334  when the channel  333  is aligned with at least a portion of the first control orifice  330 . 
         [0052]    As shown in  FIG. 9 , pressure at the valve inlet  304  continues to cause the valve head  316  to lift further from the valve seat  322  such that the spring member  338  compresses further. As such, fluid may flow from the valve inlet  304  to the valve outlet  306  and on to a manifold such as manifold  20  ( FIG. 2 ), for example. When pressure is reduced at the valve inlet  304 , the spring member  338  biases the valve body  314  toward the valve seat  322 . However, the bias force of the spring member  338  is controlled by a pressure change in the cavity  334 . For example, as the valve body  314  moves toward the valve seat  322 , a pressure is reduced in the cavity  334  causing an opposing force to the bias of the spring member  338 . In certain aspects, the second control orifice  332  facilitates fluid communication between the cavity  334  and an environment external the valve assembly  300  when the channel  333  is aligned with at least a portion of the second control orifice  332 . During such alignment, fluid may flow from the environment through the second control orifice  332  and into the cavity  334  to increase and/or equalize a pressure therein. Such flow may allow the valve body  314  to move toward the seat  322  in an accelerated manner until the fluid communication between the channel  333  and the second control orifice  332  is ceased, such as shown in  FIGS. 7 and 8 . 
         [0053]    As an illustrative example, as the linear motion of the valve body  314  changes the volume of the cavity  334 , a sudden motion of the valve body  314  is impeded by the flow dynamics of the cavity  334 . Therefore, the cavity  334  decreases the maximum impact velocity of both the strokes and return motions of the valve body  314 . As such, wear of the valve assembly  300  may be reduced and the life expectancy of the spring member  338  may be increased. 
       INDUSTRIAL APPLICABILITY 
       [0054]    The disclosed valve assemblies  100 ,  200 ,  300  may find potential utility for use with fuel pumps in internal combustion engines, and particularly to such engines utilizing high-pressure fuel systems, including compression ignition engines, such as diesel engines. 
         [0055]    In general, technology disclosed herein may have industrial applicability in a variety of settings such as in a variety of diesel engine settings in which space requirements are particularly limited. The valve assemblies  100 ,  200 ,  300  may be effective to improve fuel pressure modulation of associated engines by reducing fuel pressure variability associated with divergent placements of control valve, sensor and relief valve units. Industrial applicability of such compact fuel pump units extends to virtually all motorized transport platforms, including automobiles, buses, trucks, tractors, industrial work machines and most off-road machines utilized in agriculture, mining, and construction. 
         [0056]    The high pressure pump unit features disclosed herein may be particularly beneficial to wheel loaders and other earth moving, construction, mining or material handling vehicles that may utilize compact fuel pump systems within such fuel pump housings. Such pump unit features may also be particularly beneficial to the previously mentioned marine and industrial applications including petroleum, drilling, and electrical. 
         [0057]    It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
         [0058]    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 may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.