Abstract:
A fuel injector isolation system in a high pressure fuel injection system comprises an isolated fuel rail assembly. At least one cylinder has a cylinder head. A fuel injector is coupled to and in fluid communication with the fuel rail assembly, extends axially through an opening in the cylinder head, and is moveable within the opening in relation to the cylinder head.

Description:
FIELD OF THE INVENTION 
     The present invention relates to high pressure spark ignition direct injection (SIDI) fuel delivery, and more particularly to an attachment system for high pressure fuel injectors in an isolated SIDI fuel delivery system. 
     BACKGROUND OF THE INVENTION 
     Spark ignition direct injection (SIDI) combustion systems (and other direct injection combustion systems) for internal combustion engines provide improved fuel economy and increased power over conventional port fuel-injected combustion systems. A SIDI engine includes a high pressure fuel injection system that sprays fuel directly into a combustion chamber. The fuel is directed to a specific region within the combustion chamber. As a result, a homogeneous or stratified charge may be created in the combustion chamber as desired. Throttling requirements are less restrictive and fuel combustion characteristics are improved, thereby improving fuel economy and engine output. 
     Referring now to  FIG. 1 , an exemplary SIDI engine  10  includes an engine block  12  that includes one or more cylinders  14 . A spark plug  16  extends into a combustion chamber  18 . The combustion chamber  18  is defined by a piston  20 , the cylinder  14 , and a cylinder head  21 . The cylinder  14  includes one or more exhaust ports  22  and corresponding exhaust valves  24 . The cylinder  14  includes one or more intake ports  26  and corresponding intake valves  28 . A fuel injector  30  extends into the combustion chamber  18 . One or more of the fuel injectors  30  are connected to a fuel rail  32 . 
     Referring now to  FIGS. 1 and 2 , the fuel rail  32  provides fuel to the fuel injectors  30 . The fuel injectors  30  deliver fuel to the combustion chamber  18  according to performance requirements of the SIDI engine  10 . Typically, a low pressure (e.g. approximately 45-75 psi) fuel supply pump  40  is located within a fuel tank  42 . The low pressure fuel supply pump  40  delivers fuel to a high pressure injection pump  44 . The injection pump  44  pressurizes the fuel at approximately 750 to 2250 psi, depending on demand. The injection pump  44  provides the pressurized fuel to the fuel rail  32 . The fuel rail  32  is rigidly fastened to the cylinder head  21  of the cylinder  14 . For example, the fuel rail  32  is fastened to the cylinder head  21  via a fuel rail attachment assembly (not shown). The fuel injector  30  is rigidly fastened (e.g., clamped) between the fuel rail  32  and the cylinder head  21 , or another suitable fixture of the SIDI engine  10 . A location of the fuel injector  30  relative to the combustion chamber  18 , as well as a design of a fuel injector nozzle  46 , are optimized to achieve desired combustion characteristics. 
     SUMMARY 
     A fuel injector isolation system in a high pressure fuel injection system comprises an isolated fuel rail assembly. At least one cylinder has a cylinder head. A fuel injector is coupled to and in fluid communication with the fuel rail assembly, extends axially through an opening in the cylinder head, and is moveable within the opening in relation to the cylinder head. 
     In other features, a vehicle comprises an engine block that includes at least one combustion cylinder having a cylinder head and a combustion chamber. A high pressure fuel injection system delivers fuel directly into the combustion chamber. The high pressure fuel injection system includes an isolated fuel rail assembly and a fuel injector coupled to and in fluid communication with the fuel rail assembly that extends axially through an opening in the cylinder head and is moveable within the opening in relation to the cylinder head. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a cross-sectional view of a spark ignition direct injection (SIDI) engine cylinder according to the prior art; 
         FIG. 2  is a functional block diagram of a SIDI fuel rail assembly according to the prior art; 
         FIG. 3A  is a graphical representation of SIDI fuel system noise according to the prior art; 
         FIG. 3B  is a graphical representation of SIDI fuel system noise according to the prior art; 
         FIG. 4  is a cross-sectional view of a SIDI fuel injector arrangement according to a first implementation of the present invention; 
         FIG. 5  is a cross-sectional view of a SIDI fuel injector arrangement according to a second implementation of the present invention; 
         FIG. 6A  is a cross-sectional view of a SIDI fuel injector mounting system according to a third implementation of the present invention; 
         FIG. 6B  illustrates a retainer clip used in a SIDI fuel injector mounting system according to the present invention; 
         FIG. 6C  is a cross-sectional view of an assembled SIDI fuel injector mounting system according to the present invention; 
         FIG. 7  is a cross-sectional view of a SIDI fuel injector mounting system according to a fourth implementation of the present invention; 
         FIG. 8A  is a cross-sectional view of a SIDI fuel injector mounting system according to a fifth implementation of the present invention; 
         FIG. 8B  is a cross-sectional view of an assembled SIDI fuel injector mounting system including a retainer plate according to the present invention; and 
         FIG. 8C  is a fuel injector retainer plate according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. 
     A typical SIDI system generates undesirable noise during normal operation. As used herein, the term noise refers to any unwanted or undesirable noise that is generated during normal operation of electrical, mechanical, and/or electromechanical devices. The noise is not indicative of present and/or potential damage to these devices. As shown in  FIGS. 3A and 3B , pressure pulsations (i.e. disturbances) on a right fuel rail and a left fuel rail are indicated at  60  and  62 , respectively. Pressure fluctuations are indicated at  64  for the fuel inlet line. The pressure pulses  60 ,  62 , and  64  are synchronous with the electronic solenoid command signal  66  (e.g., from a Powertrain Control Module, or PCM) which controls the high pressure injection pump  44 . These system pressure disturbances  60 ,  62 , and  64  excite various components of the SIDI engine to radiate unwanted noise pulses as indicated at  68 ,  70 ,  72 , and  74 , for example. Sharp pressure pulses generated within the high pressure pump  44  at each pump stroke contribute to unwanted audible noise. Conventionally, the high pressure injection pump is controlled electronically. For example, the high pressure injection pump includes a reciprocating plunger in communication with an electronic governed solenoid valve that maintains the desired fuel rail (injection) pressure. The electronic signal pulses  66  control the pump&#39;s solenoid valve as dictated by the PCM. Similarly, secondary high frequency rail pressure pulses  60  and  62  are generated at each injector firing as high pressure fuel is discharged (injected) into the combustion chamber  18 . Together, the pressure impulses generated by both the pump and injectors constitute the majority of impulsive noise excitation to the engine. 
     Additionally, operation of the fuel injectors cause the SIDI system to generate noise. An impulse is generated each time the fuel injector “fires” (i.e. delivers fuel to the combustion chamber), which can be seen to be coincident with the electronic PCM signal pulses  76 . These impulses are simultaneously comprised of both electromechanical (solenoid) and electro-hydraulic forces. The fuel injectors include electronically-controlled needle valve openings. The opening and closing actuation (e.g. electromechanical and/or hydraulic actuation) of the needle valve openings cause the noise pulses  78 . 
     As described above, operation of the injection pump and the fuel injectors contribute significantly to the impulsive noise that the SIDI system generates. In particular, rigid mechanical contact between the fuel rail and the cylinder head, as well as between the fuel injector and the cylinder head, transfer noise energy between the SIDI system and various components of the engine. The present invention provides a fuel injector attachment system for high pressure SIDI fuel delivery systems that incorporate noise isolation technology. More specifically, the present invention provides a SIDI system that directly couples the fuel injectors to the fuel rail assembly and isolates elements of the fuel injectors from the cylinder head to interrupt transmission paths of noise energy. With the injector fastened to the rail in the manner described herein, the rail isolation limits vibration energy from being transmitted into the engine. 
     Referring now to  FIG. 4 , an isolated SIDI fuel injector system  100  according to the present invention is shown. A fuel injector  102  delivers fuel from an isolated fuel rail assembly  104  through a cylinder head  106  to a combustion chamber  108 . Conventionally, SIDI fuel injectors (as well as SIDI fuel rail assemblies) are rigidly mounted and/or affixed to the cylinder head  106 . In the present implementation, the fuel injector  102  is suspended from the fuel rail assembly  104  and is substantially mechanically isolated from the cylinder head  106 , especially in the axial direction. The fuel injector  102  is directly coupled to the isolated fuel rail assembly  104  via an injector cup boss  110 , an injector locating base  112 , an injector seat  114 , and a snap ring  116 . The injector seat  114  supports a posterior spherical portion  118  of the injector locating base  112 . The injector seat  114  (e.g. a split spherical seat or other suitable device) secures and maintains a desired position of the fuel injector  102  relative to the injector cup boss  110 . An O-ring  120  provides a wet seal. 
     The snap ring  116  provides additional support to maintain the desired position of the fuel injector  102 . The snap ring  116  may be removable to allow the fuel injector to be insertably coupled to and/or removed from the injector cup boss  110 . The SIDI fuel injector system  100  may also include an anterior injector seat (not shown) that contacts an upper portion of the fuel injector  102  within the injector cup boss  110 . 
     As described above, the fuel injector  102  is directly coupled to the fuel rail assembly  104  without rigid mechanical contact between the injector cup boss  110  and the cylinder head  106 . The injector seat  114  limits the axial position of the fuel injector  102  with respect to the injector cup boss  110 . In the present implementation, the injector seat  114  may be formed from an elastomeric material. Those skilled in the art can appreciate that the present invention is not limited to using elastomeric materials. Other materials, including, but not limited to, nylon, composites, and/or metals are anticipated. For example, thermal conductivity of an elastomeric material forming the injector seat  114  may be increased by the addition of aluminum particles. 
     The cylinder head  106  includes an opening  122  that accommodates the fuel injector  102  and a fuel injector nozzle  124 . In conventional SIDI systems (as described in  FIG. 1 ), there is rigid mechanical contact between the cylinder head  106  and the fuel injector  102  to maintain a position of the fuel injector. As a result, noise is transferred between the fuel injector  102  and the cylinder head  106  via contiguous axial contact. In the present implementation, the fuel injector  102  floats in the opening  122 , isolating the fuel injector  102  from the cylinder head  106 . The fuel injector  102  includes a combustion seal (e.g. a nylon or Teflon combustion seal)  126  located near the fuel injector nozzle  124 . The combustion seal  126  seals combustion gases from the combustion chamber  108  and is the only contact between the fuel injector  102  and the cylinder head. Thus, there is no metal-to-metal (i.e., rigid) contact of the injector with the cylinder head. In this manner, the isolated SIDI fuel injector system  100  eliminates substantial axial contact between the fuel injector  102  and the cylinder head  106 . 
     A biasing element, such as a spring  128 , may be included. The spring  128  provides a downward biasing force to position the fuel injector  102  within the cylinder head  106 . However, it is to be understood that a biasing element is not required for proper positioning of the fuel injector  102 . For example, an internal fuel rail pressure is typically sufficient to bias the fuel injector against the injector seat  114 . Further, although the spring  128  is shown disposed between the injector cup boss  110  and an intermediate portion  130  of the fuel injector  102 , those skilled in the art can appreciate that the spring  128  may be otherwise located. For example, the spring  128  may be located between an upper interior surface  132  of the injector cup boss  110  and an upper portion  134  of the fuel injector  102  as shown in  FIG. 5 . 
     As described above, a longitudinal position of the fuel injector  102  is maintained. In this manner, proper positioning of the fuel injector nozzle  124  for optimized combustion is maintained. Further and as indicated at  136 , the configuration of the SIDI fuel injector system  100  allows angular rotation of the fuel injector  102  relative to the cylinder head  106 . For example, the spherical portion  118  of the injector locating base  112  and the injector seat  114  allow a degree of angular latitude to compensate for misalignment and/or slight positional errors. The opening  122  is sufficiently large to accommodate angular rotation of the fuel injector  102  while maintaining isolation between the fuel injector  102  and the cylinder head  106 . A gap between the fuel injector  102  and the cylinder head  106  as indicated at  138  allows for limited longitudinal movement of the fuel injector  102 . For example, if the injector seat  114  compresses and/or the snap ring  116  is damaged, the fuel injector  102  will not necessarily contact the cylinder head  106 . For example, a controlled clearance between the bottom of the injector base and the cylinder head port acts as a failsafe in the event of a improperly-positioned or snap ring  116 . The injector is trapped between the rail and head thereby maintaining the integrity of the wet seal (i.e., the O-ring  120 ), with increased noise being the only degradation to the system. 
     The isolated fuel injector arrangements of previous implementations may be combined and/or integrated with a fuel injector mounting system  150  as shown in  FIGS. 6A ,  6 B, and  6 C. A fuel injector  152  is inserted into an injector cup boss  154  of a fuel rail assembly  156 . A retainer clip  158 , shown in  FIG. 6B  and cross-sectionally in  FIG. 6A , retains the fuel injector  152  within the injector cup boss  154 . The retainer clip  158  engages a stepped collar  160  disposed on the fuel injector  152 . As shown, the retainer clip  158  is a split-segmented snap retainer. However, those skilled in the art can appreciate that other types of retainer clips may be used. The fuel injector mounting system  150  allows for angular rotation and misalignment compensation as described in previous embodiments and facilitates attachment of the fuel injector  152  to the fuel rail assembly  156 . Any suitable tool may be applied to release the retainer clip  158  and remove the fuel injector  152 . 
     An alternative implementation of a fuel injector mounting system  170  is shown in  FIG. 7 . A fuel rail assembly  172  includes one or more fuel injector retaining interfaces (e.g. injector cup bosses)  174 . The interface  174  includes a retainer clip groove  176  that is configured to receive a retainer clip  178   a  (shown in profile at  178   b ). A fuel injector  180  is inserted within the interface  174 . An injector sleeve  182  is inserted over the fuel injector  180  and the interface  174 . The retainer clip  178   a  is inserted into one or more retainer clip slots  184  and through the retainer clip groove  176 . 
     In this manner, the retainer clip  178   a , in combination with the injector sleeve  182 , maintains an axial/longitudinal position and a radial position of the fuel injector  180 . A clearance gap  188  between the injector and cylinder head provides isolation as described in previous implementations. The features of the fuel injector mounting system  170  may be combined and/or integrated with previous implementations of the isolated fuel injectors as described in  FIGS. 4-6 . 
     Another implementation of a fuel injector mounting system  200  is shown in  FIGS. 8A ,  8 B, and  8 C. A fuel rail assembly  202  includes one or more injector retaining interfaces  204 . The interface  204  includes a retainer plate groove  206 . A fuel injector  208  is inserted into the interface  204  through an opening  210  in a retainer plate  212 . When the fuel injector  208  is suitably positioned, the retainer plate  212  slides in a direction  214  parallel to the fuel rail assembly  202  to lock the fuel injector  208  in position within the interface  204 . More specifically, a locking portion  216  of the opening  210  engages an injector retaining groove  218  of the fuel injector  208 . 
     The retainer plate  212  includes retainer clips  220 . When the retainer plate  212  is positioned to lock the fuel injector  208  in place, the retainer clips  220  engage the retainer plate grooves  206 . In this manner, the retainer plate  212  maintains a position of the fuel injector  208  as described in previous implementations. In an alternative implementation, a plurality of individual retainer plates (not shown) that correspond to a plurality of retaining interfaces  204  may replace the continuous retainer plate  212 . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.