Patent Publication Number: US-2011068194-A1

Title: Cooling structure of fuel injection valve

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention mainly relates to a cooling structure of a fuel injection valve to be applied to a diesel engine. 
     2. Description of the Related Art 
       FIG. 4  is a sectional view of a relevant part of a conventional fuel injection valve of a diesel engine. 
       FIG. 4  shows a fuel injection valve  100  in which a nozzle has an injection hole for injecting fuel at a tip thereof and a needle valve  2  is fit in the nozzle  1  such that the valve can reciprocate therein. When there is no injection, the tip of the needle valve  2  is in contact with a seating portion of the nozzle  1  so as to store high-pressure fuel in a fuel storage  5 . 
     A fuel injection valve body  16  includes a hollow space  16   a  and a spring shoe  8   a  of the nozzle valve is fit in the hollow space at a bottom thereof in such a manner that the spring shoe  8   a  is in contact with a top end  2   a  of the needle valve  2 . 
     Further, a needle valve spring  9  is interposed in the hollow space  16   a  between the spring shoe  8   a  and the injection valve body  16 . In the non-injection state, the needle valve spring  9  presses the tip of the needle valve  2  against the seating portion  5   a  of the nozzle  1 . 
     Furthermore, a spacer  15  is interposed between the injection valve body  16  and the nozzle  1 . The needle valve  2  is inserted into the spacer  15 . A fuel passage  21  is in connective communication with the fuel storage  5  through the injection valve body  16 , the spacer  15  and the nozzle  1 . 
     The top of the injection valve body  16  is pressed from above by a nozzle ground (pressing metal member not) not shown in the drawing so as to fix the fuel injection nozzle body  16  to a cylinder head. An O-shaped ring  16   b  is inserted in the space between the injection valve body  16  and the cylinder head  110 . 
     Further, a nozzle nut  3  in a shape of a sleeve supports the nozzle  1  and the spacer  15  inside thereof. The top part of the nozzle nut  3  is fixed to the injection valve body  16  on an outer circumference of the valve body  16  by screws (screw fastening sections  3   a ). A metal gasket  7  is inserted in the space under the bottom surface of the nozzle nut  3  to be attached to the nozzle nut  3 . 
     Furthermore, an outer sleeve  6  is installed around the nozzle nut  3  such as to cover the outer circumference of the nozzle nut  3  like a sleeve so that a bottom surface  6   c  of the sleeve  6  touches the cylinder head  110 . 
     In this manner, the nozzle nut  3  is fastened at the screw fastening sections  3   a  of the injection valve body  16  so that a shoulder part  1   b  of the nozzle  1  is secured between the nozzle nut  3  and the spacer  15 . 
     Further, the metal gasket  7  for heat conduction is inserted between an outer bottom surface  3   b  of the nozzle nut  3  and a top surface  6   b  of the outer sleeve  6  facing the bottom surface  3   b . The metal gasket  7  for fastening the injection valve body  16  to the cylinder head  110  is attached tightly between the outer bottom surface  3   b  of the nozzle nut  3  and the top surface  6   b  of the outer sleeve  6 . 
     The top part of the outer sleeve  6  is fit into an inner part of the cylinder head  110 , and the joint between the outer sleeve  6  and the cylinder head  110  is shaft-sealed and a shaft with an O-ring  11 . 
     To perform the fuel injection, the fuel is passed through the fuel passage  21  and stored in the fuel storage  5 , and once the pressure in the fuel storage  5  becomes higher than the downward force of the spring  9 , the needle valve  2  opens so that the high-pressure fuel stored in the fuel storage  5  is injected through the injection holes  4 . 
     In the fuel injection valve  100 , the temperature of the seating portion  5   a  of the nozzle  1  rises in response to the high load operation of the engine. To sustain the durability of the nozzle  1 , it is necessary to keep the temperature of the seating portion  5   a  below a certain temperature. However, the fuel injection valve  100  shown in  FIG. 4  has limited capability to suppress the temperature rise. 
     The injection valves to take measure against the temperature rise of the nozzle are disclosed in Patent Document 1 (JP2001-221123A) and Patent Document 2 (JP2001-41131A). 
     According to Patent Document 1, the cylinder head has a joint hole into which heat transfer member is fitted and the nozzle is tightly fitted in a through-hole of the heat transfer member so as to transfer the heat firmly from the nozzle to the cylinder heat via the heat transfer member. 
     According to Patent Document 2, an o-ring of rubber type is disposed on inner and outer circumferences of the top part of the outer sleeve which surrounds the nozzle nut so as to prevent the water getting in from the top part of the outer sleeve. 
     As described above, it is necessary in the fuel injection valve to cool the nozzle whose temperature rises in response to the high load operation of the engine. 
     In such a case that the nozzle is not directly cooled by cooling media such as cooling water, it is necessary to effectively transfer heat from the nozzle to the cylinder heat. 
     In the fuel injection valve shown in  FIG. 4 , the heat is transferred from the nozzle  1  to the cylinder head  110  via the outer bottom surface  3   b  of the nozzle nut  3 , the metal gasket  7  for heat transfer and the bottom part of the outer sleeve  6 . 
     In this case, small gap A must be provided between the outer surface of the nozzle nut  3  and the inner surface of the outer sleeve  6  so as to provide a space for assembling and disassembling of the fuel injection valve and absorbing heat expansion of the components such as the injection valve body  16  and the nozzle nut  3 . Thus, the small gap A cannot be utilized as a heat transfer surface. 
     Therefore, the fuel injection valve  100  has limited capability of suppressing the temperature rise of the nozzle in response to the high load operation of the engine and there is not enough cooling effect of the nozzle. 
     RELATED ART DOCUMENT 
     Patent Document 
     [PATENT DOCUMENT 1] JP2001-221123A 
     [PATENT DOCUMENT 2] JP2001-41131A 
     SUMMARY OF THE INVENTION 
     In view of the problems of the related art, an object of the present invention is to provide a cooling structure of a fuel injection valve which can cope with the high load operation of the engine by transferring heat efficiently from a nozzle to a cylinder head and improving the cooling effect of the fuel injection valve including the nozzle. 
     To achieve the object of the present invention, the present invention proposes a cooling structure of a fuel injection valve which comprises: a nozzle having an injection hole at a tip; a nozzle nut being formed in a shape of sleeve and supporting the nozzle in an inner circumference of the nozzle nut; an outer sleeve surrounding an outer circumference of the nozzle nut and abutting a cylinder head at a bottom surface thereof; a metal gasket interposed between a bottom surface of the nozzle nut and an opposing surface of the outer sleeve; an injection valve body being fastened to the cylinder head, the nozzle being fixed to the nozzle nut by the injection valve body, a bottom surface of the outer sleeve being fixed to the cylinder head by a fastening force of the injection valve body to the cylinder head; and a needle valve being reciprocatably fit inside the nozzle and being removably attached to a seating portion of the nozzle at a tip so as to control an opening and closing of the needle valve to inject the fuel from the injection hole, the cooling structure of the injection valve comprising a metal ring member which is interposed between an outer circumferential face of the nozzle nut and an inner circumferential face of the outer sleeve so as to transfer heat from the nozzle to the cylinder head via the nozzle nut and the outer sleeve. In this, the metal ring member may be formed into a ring shape with a notched portion in an outer circumference thereof like a piston ring or a complete circle by configuring the nozzle nut to be capable of being separated and assembled so that the metal ring member can be fit in to be installed to the nozzle nut. 
     It is preferable to install the metal ring member in such a position that the outer circumferential face of the outer sleeve is in contact with a cooling water passage of a side of the cylinder head and the metal ring member is disposed in a space of a cylindrical slit shape in vicinity to the nozzle. However, there is some restriction to the installation location depending on the shape of the outer circumferential face of the nozzle nut and the inner circumferential face of the outer sleeve  6 . For instance, the metal ring member cannot be installed where the circumferential surfaces form a taper shape. Therefore, it is preferable to install the metal ring member  10  in a space A of a cylindrical slit shape that is arranged lower than a spacer  15  interposed between the injection valve body and the nozzle. 
     Moreover, the space A extends from the outer circumference of the metal gasket  7  up to the top of the nozzle nut except for the section where the outer circumferential face of the nozzle nut tapers. As mentioned above, the metal ring member  10  may be installed in the space below the spacer  15 . 
     In the example illustrated in  FIG. 1 , the nozzle nut  3  is not in direct contact with the spacer  15  and the injection valve body  16  is fit into the upper part of the nozzle nut  3  at a screw mounting section  3   a  to be installed between the injection valve body  16  and the nozzle  1 . Therefore, it is efficient to install the metal ring member  10  in the space A of a slit shape that is arranged lower than the spacer  15  so as to efficiently cool the nozzle  1 . 
     Moreover, the metal gasket  7  can be any metal with heat conductivity such as stainless steel and more preferably copper. 
     Further, it is preferable that the heat is transferred from the nozzle to the cylinder head via both of the metal gasket and the metal ring member. 
     Furthermore, a detailed cooling structure of the fuel injection valve is described below.
     1) The metal ring member has a shape of a hollow ring, and the metal ring member is in contact with the inner circumferential face of the outer sleeve at an outer circumference thereof and with a groove formed in the outer circumferential face of the nozzle nut at an inner circumference thereof.   2) A spring is provided to press an outer circumference of the metal ring member against the inner circumferential face of the outer sleeve, the outer circumference of the metal ring member forming a contact face with the inner circumference face of the outer sleeve.   

     According to the present invention, in the fuel injection valve comprising the metal gasket interposed between the bottom surface of the nozzle nut and the opposing surface of the outer sleeve and the injection valve body being fastened to the cylinder head, by which the nozzle is fixed to the nozzle nut, the metal ring member is interposed between the outer circumferential face of the nozzle nut and the inner circumferential face of the outer sleeve so as to transfer heat from the nozzle to the cylinder head via the nozzle nut and the outer sleeve. 
     Therefore, the heat can be transferred from the nozzle to the cylinder head by the metal gasket via the bottom surfaces of the nozzle nut and the outer sleeve, and also by the metal ring member via the outer circumferential face of the nozzle nut and the inner circumferential face of the outer sleeve. In this manner, the heat can be transferred from the nozzle to the cylinder via both of the metal gasket and the metal ring member. 
     Also it is now possible to use the space between the outer circumferential face of the nozzle nut and the inner circumferential face of the outer sleeve which could not be used in the conventional case. By inserting the metal ring member lin the space between the outer circumferential face of the nozzle nut and the inner circumferential face of the outer sleeve, the faces can be utilized as heat transfer surfaces and the heat can be transferred from the nozzle to the cylinder head. 
     As described above, the heat is transferred from the nozzle to the cylinder head via both the metal gasket and the metal ring member so that in comparison to the conventional fuel injection valve of  FIG. 3 , a greater temperature drop can be expected and the nozzle can be operated at temperature not higher than the maximum allowable temperature even in the high load operation of the engine and thus the fuel injection valve that can cope with the high load operation of the engine can be obtained. 
     Further, unlike a fuel injection valve of a liquid cooling type which performs the cooling of the fuel injection valve by fuel oil or lubricant oil, no complex device such as a cooling passage is needed and the cooling performance of the fuel injection valve is improved at a low cost. 
     Furthermore, as a detailed cooling structure of the fuel injection valve, the metal ring member is formed into a ring shape with a hollow space inside such that the outer circumferential face thereof is in contact with the inner circumferential face of the outer sleeve and the inner circumferential face thereof is in contact with the groove arranged in the inner circumferential face of the nozzle nut. With this structure, by changing the shape of the metal ring member, the optimal contact pressure of the inner circumferential face and the outer circumferential face of the ring member can be obtained to transfer heat from the nozzle efficiently. 
     Moreover, as another detailed cooling structure of the fuel injection valve, the metal ring member comprises the spring which presses an outer circumference of the metal ring member against the inner circumferential face of the outer sleeve, and the outer circumference of the metal ring member forms the contact face with the inner circumference face of the outer sleeve. With this structure, by adjusting the strength of the spring which presses the contact face of the metal ring member, the optimal contact pressure can be obtained so as to transfer the heat efficiently from the nozzle  1  to the cylinder head side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  sectional view of a main part of a fuel injection valve of a diesel engine in relation to a first preferred embodiment of the present invention. 
         FIG. 2  An enlarged view of a section Z of the first preferred embodiment. 
         FIG. 3  An enlarged view of a section Z of a second preferred embodiment. 
         FIG. 4  A sectional view of a main part of a fuel injection valve of a diesel engine in relation to the conventional case. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, shape, its relative positions and the like shall be interpreted as illustrative only and not limitative of the scope of the present. 
     First Preferred Embodiment 
       FIG. 1  is a sectional view of a main part of a fuel injection valve of a diesel engine in relation to a first preferred embodiment of the present invention.  FIG. 2  is an enlarged view of a section Z of the first preferred embodiment. 
       FIG. 1  shows a fuel injection valve  100  in which a nozzle has an injection hole  4  for injecting fuel at a tip thereof and a needle valve  2  is fit in the nozzle  1  such that the needle valve can reciprocate therein. When there is no injection, the tip of the needle valve  2  is in contact with a seating portion  5   a  of the nozzle  1  so as to store high-pressure fuel in a fuel storage  5 . 
     A fuel injection valve body  16  includes a hollow space  16   a , and a spring shoe  8   a  of the nozzle valve is fit in the hollow space  16   a  at a bottom thereof in such a manner that the spring shoe  8   a  is in contact with a top end  2   a  of the needle valve  2 . 
     Further, a needle valve spring  9  is interposed in the hollow space  16   a  between the spring shoe  8   a  and the injection valve body  16 . In the non-injection state, the needle valve spring  9  presses the tip of the needle valve  2  against the seating portion  5   a  of the nozzle  1 . 
     Furthermore, a spacer  15  is interposed between the injection valve body  16  and the nozzle  1 . The needle valve  2  is inserted into the spacer  15 . A fuel passage  21  is in connective communication with the fuel storage  5  through the injection valve body  16 , the spacer  15  and the nozzle  1 . 
     The top of the injection valve body  16  is pressed from above by a nozzle ground (pressing metal member) which is not shown in the drawing, so as to fix the fuel injection nozzle body  16  to a cylinder head. An O-shaped ring  16   b  is inserted in the space between the injection valve body  16  and a cylinder head  110 . 
     The configuration listed above is the same as the conventional case illustrated in  FIG. 4 . 
     In the fuel injection unit  100 , a nozzle nut  3  is formed in a shape of sleeve and supporting the nozzle  1  and the spacer  15  in an inner circumference thereof. The top part of the nozzle nut  3  is fixed to the injection valve body  16  on an outer circumference of the valve body  16  by screws (screw fastening sections  3   a ). 
     Furthermore, an outer sleeve  6  is installed around the nozzle nut  3  such that the outer sleeve  6  surrounds the outer circumference of the nozzle nut  3  like a sleeve, and a bottom surface  6   c  thereof touches the cylinder head  110 . 
     In this manner, the nozzle nut  3  is fastened at the screw fastening sections  3   a  of the injection valve body  16  so that a shoulder part  1   b  of the nozzle  1  is secured between the nozzle nut  3  and the spacer  15 . 
     Further, a metal gasket  7  for heat conduction is inserted between an outer bottom surface  3   b  of the nozzle nut  3  and a top surface  6   b  of the outer sleeve  6  facing the bottom surface  3   b . By fitting the injection valve body  16  in the nozzle nut  3  at the screw fastening section  3   a , the metal gasket  7  is attached tightly between the outer bottom surface  3   b  of the nozzle nut  3  and the top surface  6   b  of the outer sleeve  6 . The metal gasket  7  may be any metal with heat conductivity. 
     A metal ring member  10  is interposed between an outer circumferential face  3   c  of the nozzle nut  3  and an inner circumferential face  6   t  of the outer sleeve  6  so as to transfer heat from the nozzle  1  to the cylinder head  110  via the nozzle nut  3  and the outer sleeve  6 . 
     Moreover, a small gap A is provided between the outer circumferential face  3   c  of the nozzle nut  3  and the inner circumferential face  6   t  of the outer sleeve  6  in the same manner as the conventional case so as to provide a space for assembling and disassembling the fuel injection valve  100  and for absorbing heat expansion of the components such as the fuel injection valve body  16  and the nozzle nut  3 . Therefore, the outer circumferential face  3   c  and the outer circumferential face  6   t  can be utilized as heat transfer surfaces by providing the metal ring member  10 . 
     In the first preferred embodiment, as illustrated in  FIG. 2 , the metal ring member  10  is inserted in a groove  120  and has a shape of a hollow ring with a hollow space  10   a , and the metal ring member  10  is in contact with an inner circumferential face  6   f  of the outer sleeve  6  at an outer circumference  10   c  thereof and with the groove  120  formed in the outer circumferential face of the nozzle nut  3  at an inner circumference thereof. On the inner circumferential face, a communication path  10   b  having a opening width C is provided to open the hollow space  10   a  to outside. 
     In this manner, the heat can be transferred from the nozzle  1  to the cylinder head  110  via the metal ring member  10  with a hollow space. Further, by changing the shape of the metal ring member, the optimal contact pressure of the inner circumferential face and the outer circumferential face of the ring member  10  can be obtained to transfer the heat from the nozzle efficiently. Furthermore, by adjusting the opening width C of the communication path  10   b , the contact pressure can be adjusted. 
     Moreover, the metal ring member  10  can be any metal with heat conductivity. 
     The top part of the outer sleeve  6  is fit into an inner part of the cylinder head  110 , and the joint between the outer sleeve  6  and the cylinder head  110  is shaft-sealed and a shaft with an O-ring  11 . 
     To perform the fuel injection, the fuel is passed through the fuel passage  21  and stored in the fuel storage  5 , and once the pressure in the fuel storage  5  becomes higher than the downward force of the needle valve spring  9 , the needle valve  2  opens so that the high-pressure fuel stored in the fuel storage  5  is injected through the injection hole  4 . 
     According to the first preferred embodiment, the injection valve  100  comprises the metal gasket  7  interposed between the bottom surface of the nozzle nut  3  and the opposing surface of the outer sleeve  6 , and the fuel injection valve body  16  being fastened to the cylinder head  110 , and the nozzle  1  is fixed to the nozzle nut  3  by the injection valve body  16 . Further, the metal ring member  10  is provided between the outer circumferential face  3   c  of the nozzle nut  3  and the inner circumferential face  6   t  of the outer sleeve  6  so as to transfer heat from the nozzle  1  to the cylinder head  110  via the nozzle nut  3  and the outer sleeve  6 . 
     With the above structure, the heat can be transferred from the nozzle  1  to the cylinder head  110  by the metal gasket  7  via the nozzle nut  3  and the bottom surface of the outer sleeve  6 . Furthermore, the heat can also be transferred from the nozzle  1  to the cylinder head  10  by the metal ring member  10  arranged between the outer circumferential face of the nozzle nut  3  and the inner circumferential face of the outer sleeve  6 . Therefore, the heat can be transferred from the nozzle to the cylinder heat at two places, i.e. the metal gasket  7  and the metal ring member  10 . Also it is now possible to use the space between the outer circumferential face of the nozzle nut  3  and the inner circumferential face of the outer sleeve  6  (the gap A) which could not be used in the conventional case. By inserting the metal ring member  10  in the space between the outer circumferential face of the nozzle nut  3  and the inner circumferential face of the outer sleeve  6 , the faces can be utilized as heat transfer surfaces and the heat can be transferred from the nozzle  1  to the cylinder head  110 . 
     As described above, by transferring the heat from the nozzle  1  to the cylinder head  110  at two places, i.e. the metal gasket  7  and the metal ring member  10   a , a greater temperature drop can be expected in comparison to the conventional injection valve of  FIG. 3 . Further, the nozzle  1  can be operated at temperature not higher than the maximum allowable temperature even in the high load operation of the engine and thus the fuel injection valve  100  that can cope with the high load operation of the engine can be obtained. 
     Second Preferred Embodiment 
     A second preferred embodiment of the present invention is different from  FIG. 1  in the configuration of the metal ring member. 
       FIG. 3  is an enlarged view of a section Z of a second preferred embodiment. 
     In  FIG. 3 , a metal ring member  10   s  is formed into a ring shape with a notched portion in an outer circumference thereof like a piston ring. The cross sectional shape of the metal ring member  10   s  is square. The metal ring member  10   s  is inserted in the groove  120  such that the outer part thereof touches the inner circumferential face  6   f  of the outer sleeve  6  to form a contact face  10   m.    
     Furthermore, a spring  13  for pressing the contact face  10   m  against the inner circumferential face  6   f  of the outer sleeve  6  and another spring  12 , e.g. a plate type spring for pressing the ring member  10   s  in the length direction thereof. 
     In this manner, by adjusting the strength of the springs  12  and  13  which press the contact face  10   m  of the metal ring member  10   s , the optimal contact pressure can be obtained so as to transfer the heat efficiently from the nozzle  1  to the cylinder head  110  side. 
     Moreover, the metal ring member  10   s  can be any metal with heat conductivity. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, the heat can be efficiently transferred from the nozzle to the cylinder head. By this, the cooling effect of the fuel injection valve including the nozzle can be improved and thus the cooling structure of the fuel injection valve to cope with the high load and high rotation of the engine can be provided.