Patent Publication Number: US-10323615-B2

Title: Fuel pump apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 USC 371 of PCT Application No. PCT/EP2016/061380 having an international filing date of May 20, 2016, which is designated in the United States and which claimed the benefit of GB Patent Application No. 1508608.5 filed on May 20, 2015, the entire disclosures of each are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to fuel pump apparatus. More particularly, but not exclusively, the present disclosure relates to a hydraulic head assembly; to a pump comprising a hydraulic head assembly; and to an adapter for a hydraulic head assembly. 
     BACKGROUND 
     A known fuel-lubricated pump P 1  adapted to supply fuel to a fuel injection system for an internal combustion engine is shown in  FIG. 1 . The fuel-lubricated pump P 1  relies on the fuel being pumped as a lubricating medium. The fuel-lubricated pump P 1  is configured to supply diesel fuel at high pressure to a common rail (not shown) connected to a plurality of fuel injectors. The fuel-lubricated pump P 1  comprises a hydraulic head assembly  101  disposed in a pump housing H 1 . As shown in  FIG. 2 , the hydraulic head assembly  101  comprises a hydraulic head  102  having a body  103  and a turret  104 . The turret  104  comprises a cylindrical projection formed integrally with the body  103 . A first bore  105  and a pumping chamber  106  are formed in the hydraulic head  102 . The first bore  105  has a longitudinal axis X and extends through the turret  104 . The pumping chamber  106  has a larger diameter than the first bore  105 . A pumping element  107  in the form of a plunger is disposed in said first bore  105  to pressurise fuel in the pumping chamber  106 . The pumping element  107  cooperates with a rotating cam via a roller shoe assembly to cause the pumping element  107  to reciprocate within the first bore  105 . An inlet valve  108  is provided for controlling the introduction of fuel into the pumping chamber  106 . The inlet valve  108  comprises an inlet valve member  109  arranged to cooperate with an inlet valve seat  110 . A first spring element  111  cooperates with the inlet valve member  109 . An outlet valve  112  is provided for controlling the expulsion of fuel from the pumping chamber  106  to the common rail. The outlet valve  112  comprises an outlet valve member  113  arranged to cooperate with an outlet valve seat  114 . A second spring element  115  is provided to bias the outlet valve member  113  into a seated position in said outlet valve seat  114 , thereby closing the outlet valve  112 . The outlet valve  112  is opened when the pressure of the fuel in the pumping chamber  106  overcomes the spring bias applied to the outlet valve member  113  by the second spring element  115  and the fuel pressure in the common rail. The first bore  105  and the pumping element  107  are sized to form a first seal  116 . The first seal  116  is a high pressure seal and has a high pressure leakage control length L 2  which is extended by the turret  104 . 
     A limitation of the fuel-lubricated pump P 1  is a potential lack of robustness to poor lubricity fuels, for example due to different grades of fuel available in different territories. A further potential limitation is in the length of the high pressure leakage control length L 2  due to the need accurately to machine the inlet valve seat  110  over the length L 1 . 
     It is known to provide a fuel pump with a lubricating medium, typically oil, which is maintained separate from the fuel. A known oil-lubricated pump P 2  is shown in  FIG. 3 . The oil-lubricated pump P 2  is configured to supply diesel fuel at high pressure to a common rail (not shown) connected to a plurality of fuel injectors. The oil-lubricated pump P 2  comprises a hydraulic head assembly  201  disposed in a pump housing H 2 . As shown in  FIG. 4 , the hydraulic head assembly  201  comprises a hydraulic head  202  having a body  203  and a turret  204 . A first bore  205  and a pumping chamber  206  are formed in the hydraulic head  202 . The pumping chamber  206  has a larger diameter than the first bore  205 . A pumping element  207  in the form of a plunger is disposed in said first bore  205  to pressurise fuel in the pumping chamber  206 . The pumping element  207  cooperates with a rotating cam via a roller shoe assembly (not shown) to cause the pumping element  207  to reciprocate within the first bore  205 . An inlet valve  208  is provided for controlling the introduction of fuel into the pumping chamber  206 . The inlet valve  208  comprises an inlet valve member (not shown) arranged to cooperate with an inlet valve seat  210 . An outlet valve  212  is provided for controlling the expulsion of fuel from the pumping chamber  206  to the common rail. The outlet valve  212  comprises an outlet valve member  213  arranged to cooperate with an outlet valve seat  214 . The first bore  205  and the pumping element  207  are sized to form a first seal  216  and a second seal  217 . The first seal  216  is a high pressure seal and has a high pressure leakage control length L 2 . The second seal  217  is a low pressure seal and has a low pressure leakage control length L 3 . A third seal  218  in the form of a polytetrafluoroethylene (PTFE) lip seal is disposed below the second seal  217 . An annular chamber  219  and a return line  220  are formed in the hydraulic head  202  between the first and second seals  216 ,  217 . The second seal  217  functions as a back-up seal for the third seal  218 . The oil-lubricated pump P 2  can be assembled to form a direct unit pump (DUP) which is located directly into an engine block. The hydraulic head assembly  201  can also be disposed in a cam box to form an oil lubricated pump, as shown in  FIG. 3 . 
     The high pressure leakage control length L 2  of the first seal  216  must be sufficient to maintain pumping efficiency; and the low pressure leakage control length L 3  must be of sufficient length to inhibit mixing of oil into the fuel. However, the need accurately to machine the inlet valve seat  210  restricts the high and low pressure leakage control lengths L 2 , L 3  of the first and second seals  216 ,  217 . 
     The oil-lubricated pump P 2  provides improved robustness to different grades of fuel. Nonetheless, production volumes of oil-lubricated pumps are expected to remain relatively low. The lower production volumes reduce the economies of scale for production of the oil-lubricated pump P 2 . This is particularly problematic in view of the need for a specific design of hydraulic head  202 . 
     It is against this backdrop that the present invention has been conceived. At least in certain embodiments, the present invention seeks to overcome or ameliorate at least some of the problems associated with known fuel pumps. 
     SUMMARY OF THE INVENTION 
     Aspects of the present invention relate to a hydraulic head assembly. More particularly, but not exclusively, the present invention relates to a hydraulic head assembly having an adapter; to a pump comprising a hydraulic head assembly; and to an adapter for a hydraulic head assembly. 
     According to a further aspect of the present invention there is provided a hydraulic head assembly comprising:
         a hydraulic head having a first bore and a pumping chamber;   an adapter having a second bore, the adapter being connected to said hydraulic head such that said first and second bores form a substantially continuous pumping element bore; and   a pumping element disposed within said pumping element bore for pressurising fuel in the pumping chamber;   wherein a first seal is formed between the pumping element and the hydraulic head; and a second seal is formed between the pumping element and the adapter. The adapter enables the hydraulic head to be used with a separate lubricating medium, such as oil. The first seal is operative to reduce or inhibit leakage of fuel from the pumping chamber. The second seal is operative to reduce or inhibit leakage of the separate lubricating medium past the pumping element.       

     The hydraulic head can comprise a body and a turret. The first bore can extend through the turret and into the body. The turret can be a cylindrical projection from said body. The adapter can be connected to said turret. 
     The adapter can comprise a mounting section for mounting the adapter to the hydraulic head. The mounting section can comprise a collar for cooperating with the turret. The collar can be an interference fit with an external sidewall of the turret. 
     The first seal can be a high pressure seal. The second seal can be a low pressure seal. 
     The adapter can comprise a polymeric seal for cooperating with the pumping element. The polymeric seal can, for example, be a polytetrafluoroethylene (PTFE) seal. 
     A leakage path can be formed between the turret and the adapter. A collection chamber can be provided in communication with the leakage path. 
     The adapter can comprise a backleak bore. The backleak bore can extend transversely through the adapter. 
     According to a further aspect of the present invention there is provided a fuel pump comprising one or more hydraulic head assembly of the type described herein. 
     The fuel pump can comprise a plurality of said hydraulic head assemblies. The hydraulic head assemblies can be arranged in an in-line configuration. The fuel pump can, for example, comprise first and second hydraulic heads and adapters arranged in series. 
     According to a further aspect of the present invention there is provided an adapter for a hydraulic head assembly, the adapter comprising:
         a mounting section for mounting the adapter to a hydraulic head; and   a sealing section having a first bore formed therein for receiving a pumping element, the sealing section being adapted to form at least one seal with said pumping element;   wherein the adapter is configured such that, when mounted to the hydraulic head, the first bore aligns with a second bore formed in the hydraulic head to form a substantially continuous pumping element bore.       

     The sealing section can be adapted to form a low pressure seal with the pumping element. 
     The sealing section can comprise a polymeric seal for cooperating with the pumping element. 
     Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: 
         FIG. 1  shows a sectional view of a known fuel-lubricated pump for supplying high pressure fuel to a fuel injection system; 
         FIG. 2  shows a hydraulic head assembly of the fuel-lubricated pump shown in  FIG. 1 ; 
         FIG. 3  shows a sectional view of a known oil-lubricated pump for supplying high pressure fuel to a fuel injection system; 
         FIG. 4  shows a hydraulic head assembly of the oil-lubricated pump shown in  FIG. 3 ; 
         FIG. 5  shows a hydraulic head assembly comprising an adapter in accordance with an embodiment of the present invention; 
         FIG. 6  shows the hydraulic head assembly shown in  FIG. 5  used in combination with an oil-lubricated pump; and 
         FIG. 7  shows a fuel pump comprising first and second hydraulic heads and adapters in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A hydraulic head assembly  1  in accordance with an embodiment of the present invention will now be described with reference to  FIG. 5 . The hydraulic head assembly  1  is for use with an oil-lubricated pump P 2  for supplying high pressure fuel to a fuel injection system (not shown). In particular, the hydraulic head assembly  1  is configured to be mounted to a pump housing H 2  of the oil-lubricated pump P 2 . The oil-lubricated pump P 2  is adapted to supply diesel fuel to a high pressure common rail connected to a plurality of fuel injectors for injecting fuel into a combustion chamber of an internal combustion engine. 
     The hydraulic head assembly  1  comprises a hydraulic head  2  which is the same as the hydraulic head  102  of the fuel-lubricated pump P 1  described herein with reference to  FIGS. 1 and 2 . The hydraulic head  2  comprises a body  3  and a turret  4 . The turret  4  in the present embodiment comprises a cylindrical projection. A first bore  5  having a longitudinal axis X is formed in the hydraulic head  2 . A pumping chamber  6  is also formed in the hydraulic head  2 . The pumping chamber  6  is generally cylindrical and has a central axis arranged coaxially with the longitudinal axis X. The pumping chamber  6  has a larger diameter than the first bore  5 . The first bore  5  extends through the turret  4  such that the longitudinal axis X of the first bore  5  is coincident with a central longitudinal axis of the turret  4 . A pumping element  7  in the form of a plunger is disposed in said first bore  5  to pressurise fuel in the pumping chamber  6 . The pumping element  7  cooperates with a rotating cam via a roller shoe assembly to cause the pumping element  7  to reciprocate along the longitudinal axis X of the first bore  5 . An inlet valve  8  is provided for controlling the introduction of fuel into the pumping chamber  6 . The inlet valve  8  comprises an inlet valve member  9  arranged to cooperate with an inlet valve seat  10 . A first spring element  11  cooperates with the inlet valve member  9 . An outlet valve  12  is provided for controlling the expulsion of fuel from the pumping chamber  6  to the common rail. The outlet valve  12  comprises an outlet valve member  13  arranged to cooperate with an outlet valve seat  14 . A second spring element  15  is provided to bias the outlet valve member  13  into a seated position in said outlet valve seat  14 , thereby closing the outlet valve  12 . The outlet valve  12  is opened when the pressure of the fuel in the pumping chamber  6  overcomes the spring bias applied to the outlet valve member  13  by the second spring element  15  and the fuel pressure in the common rail. The first bore  5  and the pumping element  7  are sized to form a first seal  16 . The first seal  16  is a high pressure seal and has a high pressure leakage control length L 2 , as shown in  FIG. 5 . The first seal  16  reduces or inhibits leakage of fuel from the pumping chamber  6 . 
     The hydraulic head assembly  1  comprises an adapter  21  for adapting the hydraulic head  102  of a fuel-lubricated pump P 1  (as described with reference to  FIGS. 1 and 2 ) for use with an oil-lubricated pump P 2  (as described with reference to  FIGS. 3 and 4 ). The adapter  21  allows the hydraulic head  2  to be used with a separate supply of lubricating medium, such as oil. Accordingly, the adapter  21  can be referred to as a hydraulic head adapter. The adapter  21  is in the form of a sleeve connected to the turret  4 . The adapter  21  comprises a mounting section  22  and a sealing section  23 . The mounting section  22  comprises a collar  24  which is cylindrical and locates around the turret  4 . An internal sidewall  25  of the collar  24  forms an interference fit with an external sidewall  26  of the turret  4 . An upper portion of the external sidewall  26  comprises a first annular band  27  having an enlarged diameter for engaging the internal sidewall  25  of the collar  24  to form a first interference joint  28 . A lower portion of the internal sidewall  25  comprises a second annular band  29  having a reduced diameter for engaging the external sidewall  26  of the turret  4  to form a second interference joint  30 . 
     The sealing section  23  comprises a second bore  31  having the same diameter as the first bore  5 . The first and second bores  5 ,  31  are disposed coaxially along the longitudinal axis X. The first and second bores  5 ,  31  thereby form a continuous pumping element bore  32  for receiving the pumping element  7 . The pumping element  7  and the second bore  31  are sized to form a second seal  17 . The second seal  17  is a metal-to-metal close clearance seal which is equivalent to the second seal  217  of the oil-lubricated pump P 2  described herein. The second seal  17  is a low pressure seal and has a low pressure leakage control length L 3 . The second seal  17  reduces or inhibits leakage of oil past the pumping element. A third seal  18  in the form of a polytetrafluoroethylene (PTFE) lip seal is disposed below the second seal  17 . The second seal  17  is a back-up for the third seal  18  to ensure that the oil does not mix with the fuel being pumped. It will be appreciated that the sealing section  23  can be modified depending on the sealing requirements of a particular application. Specific applications may, for example, have different dilution requirements and/or packaging requirements. The configuration of the second and third seals  17 ,  18  can be modified to meet the requirements of a particular application. 
     With reference to  FIG. 6 , the hydraulic head assembly  1  in accordance with the present invention is shown in use in an oil-lubricated pump P 2 . In the present embodiment, the hydraulic head  2  is disposed in a mounting aperture  33  formed in the pump housing H 2 . A collection chamber  35  is defined by the turret  4 , the adapter  21  and the pump housing H 2 . In use, the collection chamber  35  collects any leakage between the turret  4  and the adapter  21  (represented by a dashed arrow in  FIG. 5 ). The collection chamber  35  is sealed at its upper end by an interface between the pump housing H 2  and a gasket face  36  formed on an underside of the body  3 ; and at its lower end by an interface between an O-ring  37  and the pump housing H 2 . The O-ring  37  is located in a locating channel  38  integrally formed with the mounting section  22  of the adapter  21 . The fuel collected in the collection chamber  35  is returned to a tank (not shown) via a backleak return line (not shown). 
     The adapter  21  is fitted to the hydraulic head  2  after completion of the machining of the inlet valve seat  10 . In order to accommodate the adapter  21 , certain modifications are made to the hydraulic head  2  during the manufacturing process. In particular, the hydraulic head  2  requires additional hard stage operations to the external sidewall  26  of the turret  4  to permit the interference fit with the adapter  21 . After the adaptor  21  has been fitted, a finishing operation is performed on an interior of the first and second bores  5 ,  31  to form a continuous pumping element bore in which the pumping element  7  reciprocates. This finishing operation helps to ensure that the required concentricity and bore geometries are maintained between the first and second bores  5 ,  31 . 
     It will be appreciated that the adapter  21  in accordance with the present invention enables the same hydraulic head  2  to be used for both fuel- and oil-lubricated pumps. A second seal  17  can be incorporated into the adapter  21  to provide a low pressure back-up seal without compromising the machining capability of the inlet valve  8 . Furthermore, the adapter  21  can be modified to fit various pump configurations. At least in certain embodiments, the hydraulic head assembly  1  of the present invention can have a reduced package size when compared to the oil-lubricated pump P 2  described herein. A reduction in the height of the hydraulic head assembly  1  by approximately 20 mm (measured from a driveshaft axis to the top of the hydraulic head) is achievable. 
     The oil-lubricated pump P 2  has a single pumping chamber  6 . However, the adapter  21  described herein can be modified for an in-line oil-lubricated pump P 3  comprising a plurality of pumping chambers  6 . With reference to  FIG. 7 , the in-line oil-lubricated pump P 3  comprises first and second hydraulic head assemblies  1 - 1 ,  1 - 2  disposed in a pump housing H 3 . The first and second hydraulic head assemblies  1 - 1 ,  1 - 2  have respective first and second hydraulic heads  2 - 1 ,  2 - 2  arranged in series. A first adapter  21 - 1  and a second adapter (not shown) are associated with the respective first and second hydraulic heads  2 - 1 ,  2 - 2 . The first and second hydraulic heads  2 - 1 ,  2 - 2  and the first and second adapters  21 - 1 ,  21 - 2  are mounted in the pump housing H 3 . A supply line  39  formed in the pump housing H 3  connects the first and second hydraulic heads  2 - 1 ,  2 - 2  to an inlet metering valve  40 . 
     The first and second hydraulic heads  2 - 1 ,  2 - 2  define respective first and second pumping chambers  6 - 1 ,  6 - 2 . The first and second hydraulic heads  2 - 1 ,  2 - 2  are a variant of the hydraulic head  2  described herein with reference to  FIGS. 5 and 6  and like reference numerals are used for like components. Similarly, the first and second adapters  21 - 1 ,  21 - 2  are modified versions of the adapter  21  described herein and like reference numerals are again used for like components. The first and second adapters  21 - 1 ,  21 - 2  have the same configuration and only the first adapter  21 - 1  will be described for the sake of brevity. 
     The first adapter  21 - 1  forms a first fuel annulus  41 - 1  for receiving a metered supply of fuel from the inlet metering valve  40 . An annular recess  42  formed in an outer sidewall of the first adapter  21 - 1  forms the first metered fuel annulus  41 - 1 . The first fuel annulus  41 - 1  is connected to the inlet metering valve  40  by the supply line  39 . A vertical bore  43  extending through the pump housing H 3  and a bore (not shown) in the first hydraulic head  2 - 1  connects the first fuel annulus  41 - 1  with the inlet valve  8 . A cross-drilling formed in the first adapter  21 - 1  opens at the interface between the first hydraulic head  2 - 1  and the first adapter  21 - 1  to form a backleak return line  44 . A corresponding return line  45  formed in the pump housing H 3  returns leakage fuel to a tank or reservoir. This arrangement seals the leaked high pressure fuel. A further modification of the first adapter  21 - 1  is to provide first and second O-rings  37 - 1 ,  37 - 2  for forming a seal between the adapter  21  and the pump housing H 3 . 
     It will be appreciated that various changes and modifications can be made to the hydraulic head assembly  1  and the adapter  21  described herein without departing from the scope of the present invention.