Abstract:
A valve seat  14  having an injection hole  14   b  is fixed at one end of a hollow valve main body  15 , a valve body  12  slidably supported so as to be separated from and brought into contact with the valve seat  14  to open and close the injection hole  14   b  and a swirler  16  for surrounding the valve body  12  to slidably support the valve body  12  and for imparting a swirling motion to fuel flowing into the injection hole  14   b  are equipped, a swirling groove  16   b  in the swirler  16  includes a curvature part  16   b   3  in a groove outlet, and a sectional configuration of the swirling groove  16   b  is constituted so that the depth of the central part is larger than the depth of the end part.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a fuel injection valve for cylinder injection and, more particularly, to a fuel injection valve which imparts swirling energy to a fuel flow by a swirling means, and injects a fuel from a fuel injection hole. 
   2. Description of the Related Art 
   In the conventional fuel injection valve, outlets of downstream of swirling grooves are opened around a general whole circumference of a inner circumferential annular groove of a swirler, a swirling flow is generated around a whole circumference by reducing spaces between adjacent swirling grooves, and a fuel is flowed to a injection hole in downstream so that a gap of a flow is not generated (for example, see the Japanese Patent Publication (unexamined) No. 1997/47208). 
   Since the conventional fuel injection valve is constructed as mentioned above, six swirling grooves are disposed by equal intervals, and adjacent swirling grooves are constructed so as to have a cross angle of 60°. Therefore a problem exists in that a loss of a flow occurs, and it is not possible to promote to atomize a spray since fuel getting out of swirling grooves collide at an angle of 60° to each other. 
   SUMMARY OF THE INVENTION 
   The present invention has been made to solve the above-discussed problems and has an object to reduce a loss of a flow of a fuel injection valve, and to promote to atomize a spray. Furthermore the present invention has an object to mass-produce elaborate fuel injection valves. 
   A fuel injection valve of the present invention includes a hollow valve main body, a valve seat provided at one end of the valve main body and having an injection hole, a valve body slidably supported so as to be separated from and brought into contact with the valve seat to open and close the injection hole, and a swirler for surrounding the valve body to slidably support the valve body and for imparting a swirling motion to fuel flowing into the injection hole. In this fuel injection valve, a swirling groove in the swirler is provided with a curvature part in a groove outlet, and a sectional configuration of the swirling groove is constituted so that the depth of the central part is larger than the depth of the end part. 
   In this fuel injection valve of above construction, the loss caused by collision of fuel in the outlets of the swirling grooves is reduced, therefore it is possible to promote to atomize fuel spray, and to improve combustibility of an engine. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view showing a fuel injection valve according to Embodiment 1 of the present invention; 
       FIG. 2  is a sectional view showing a end part of the fuel injection valve; 
       FIG. 3  is a sectional view taken along the line A-A of  FIG. 1 ; 
       FIG. 4  is a perspective view taken in a bottom face of a swirler; 
       FIG. 5  is a sectional view showing a configuration of a swirling groove; 
       FIG. 6  is a plane view showing a swirler; 
       FIG. 7  is a front view showing a swirler; 
       FIG. 8  is a sectional view showing a configuration of a swirling groove; 
       FIG. 9  is a front view showing a method for processing a end face; 
       FIG. 10  is a front view showing a swirler; and 
       FIG. 11  is a sectional view showing a configuration of a swirling groove; 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiment 1 
   An embodiment according to this invention is hereinafter described referring to the accompanying drawings. 
     FIG. 1  is a sectional view showing a fuel injection valve according to Embodiment 1 of the present invention,  FIG. 2  is a sectional view showing a end part of the fuel injection valve,  FIG. 3  is a sectional view taken along the line A-A of  FIG. 1 , and  FIG. 4  is a perspective view taken in a bottom face of a swirler. 
   A fuel injection valve  1  is constituted by a solenoid device  2  and a valve device  11 . The solenoid device  2  is constituted by a housing  3  serving as a yoke portion of a magnetic circuit, a stator core  4  serving as a magnetic circuit, a coil  5 , a spring  6 , a rod  7  fixed for adjusting a position of the spring  6 , rubber rings  8 ,  9  for sealing a fuel, and a metal ring  10  having a seal face of the rubber rings  8 ,  9 . 
   The valve device  11  is constituted by a valve body  12  being a needle valve, a movable core  13  integrally formed with the valve body  12 , a valve seat  14 , a hollow valve main body  15  housing the valve body  12 , and a swirler  16  imparting a swirling motion to a fuel. 
   When an actuating signal is fed to a drive circuit of the fuel injection valve  1  from a microcomputer of an engine, a current flows in the coil  5  and a magnetic flux is generated in a magnetic loop constituted by the housing  3 , the movable core  13 , and the stator core  4 . And the movable core  13  is attracted to the stator core  4  side by an electromagnetic attractive force beyond a pressing force of the spring  6 . 
   The valve body  12  integrally formed with the movable core  13  is separated from a seat portion  14   a  of the valve seat  14 , and a gap is formed between the valve body  12  and the seat portion  14   a . Next a high pressure fuel more than 2 MPa is injected from an injection hole  14   b  of the valve seat  14 , an injection of a fuel is started. When a current is not fed to the coil  5 , the valve body  12  comes in contact with the seat portion  14   a , and an injection is finished. 
   A fuel is fed from the upper portion of the fuel injection valve  1 , and flows into the inner part of the valve main body  15  through the inner part of the stator core  4 . And a fuel gets to swirling grooves  16   b  via a through hole  16   a  of the swirler  16 , and passes the seat portion  14   a through a clearance part  16   c  being a groove outlet part between the valve body  12  and the swirler  16 . Furthermore a fuel helically swirls in the injection hole  14   b , thereafter a fuel is injected toward the outside. As depicted in  FIG. 3 , curvature parts  16   b   3  are curved where the grooves  16   b  meet the clearance part  16   c  i.e., the distal end portion  16   b   4 . The curvature parts  16   b   3  are also curved at a portion near the distal end portion  16   b   4 . As shown in  FIG. 3 , the curvature parts  16   b   3  are bent to form a curve  16   b   5  on one side of the groove, behind the distal end. 
     FIG. 5  is a sectional view showing a configuration of the swirling groove  16   b . A sectional configuration of the swirling groove  16   b  is constituted so that the depth of the central part is larger than the depth of the end part. 
   That is, the swirling groove  16   b  is provided with a flat part  16   b   1  in the bottom face, and with an arc part  16   b   2  in its circumference, the swirling groove  16   b  is formed into a semicircular style. The main stream of a fuel flows in the flat part  16   b   1  that is the deepest part of the swirling groove  16   b.    
   In the groove outlets, the swirling grooves  16   b  are provided with curvature parts  16   b   3  folded to a direction in which the center line of the swirling groove  16   b  approaches the central axis of the swirler  16 , the direction of the fuel stream is changed in accordance with transverse positions of the swirling groove  16   b.    
     FIG. 6  is a plane view showing a state of the fuel stream in the swirling grooves  16   b . In transverse positions of the swirling groove  16   b , in using e 1  to e 3 , f 1  to f 3 , and g 1  to g 3  as elements of each fuel stream, the streams f 1  and f 3  flow in the arc part  16   b   2 , the groove is shallow, and stream is slow. The stream f 2  flows in the flat part  16   b   1 , the groove is deep, and stream is rapid. The rapid stream f 2  is indicated by a longer arrow than the slow streams f 1  and f 3 . 
   The direction of stream becomes different while the position of stream is changed from f 1  to f 3 , the direction of stream is changed so that the direction of the stream f 3  approaches the central axis of the fuel injection valve  1  in comparison with the stream f 1 . 
   Outlets of the swirling grooves  16   b  are opened on the same circle  16   d , the length of an arc part  16   e  between the swirling grooves  16   b  is set below fifth of the groove width  16   f.    
   That is, by reducing the spaces between outlets of the swirling grooves  16   b , and by possibly generating swirling stream of a fuel around the whole circumference of the same circle  16   d , it is possible to prevent a swirling stream in circumferential direction into the below injection hole  14   b  from breaking off. 
   By constructing as described above, it is possible to prevent a spray from breaking off, and to improve quality of a spray. Furthermore it is possible to prevent a swirling stream from breaking off into the injection hole  14   b , and to prevent parts in which carbon deposit is not washed from occurring. 
   Fuel streams getting out of adjacent swirling grooves  16   b  collide at the groove outlet parts  16   c . However, in the present invention, the curvature parts  16   b   3  are disposed near outlets of the swirling grooves  16   b , thereby the collision angle θ 1  between directly colliding fuel stream elements e 3  and f 1  is smaller than the cross angle of the swirling grooves  16   b , that is to say, the cross angle θ 2  between stream elements e 2  and f 2 . Eventually, the loss caused by collision is reduced. 
   In fuel stream elements e 3  and f 1 , the speed of fuel stream is slow, therefore the loss caused by collision is reduced. 
   As described above, according to this embodiment, the loss caused by collision of fuel in the outlets of the swirling grooves  16   b  is reduced, therefore it is possible to promote to atomize fuel spray, and to improve combustibility of an engine. 
   Embodiment 2 
   In the present embodiment, the depth of the swirling groove  16   b  is finished into the predetermined depth by processing the end face of the swirler  16 .  FIG. 7  is a front view showing a state of the swirler  16  before processing its end face,  FIG. 8  is a sectional view showing a configuration of the swirling groove  16   b  before processing.  FIG. 9  is a front view showing a method for processing the end face, the end face is processed by rotating a grinder  21 .  FIG. 10  is a front view showing a state of the swirler  16  after processing its end face,  FIG. 11  is a sectional view showing a configuration of the swirling groove  16   b  after processing. 
   In the drawings, in this embodiment, the height of a circular flat face  16   r  on the outer circumference side above the swirling groove  16   b  and the height of the flat part  16   b   1  are formed into the same height H 1 , and an end face  16   s  of the swirler  16  is ground. The height of the end face  16   s  is indicated by H 2 . 
   As shown in  FIG. 7 , the swirler  16  is formed by metal injection molding, thereafter the end face  16   s  of the swirler  16  is finished by grinding as shown in  FIG. 9 , subsequently the depth of the swirling groove  16   b  is formed into the aim dimension L 2  of a finished product from L 1  as shown in  FIG. 10  and  FIG. 11 . 
   In the present invention, a configuration of the swirling groove  16   b  is constituted so that the center becomes deep, the central bottom part of the swirling groove  16   b  is provided with the flat part  16   b   1 , and the flat face having the same height as the flat part  16   b   1  is formed on the outside of the swirling groove  16   b . The flat part  16   b   1  of the swirling groove  16   b  and the circular flat face  16   r  on the outside of the swirling groove  16   b  are formed into the same flat face by using the same die. 
   In processing the end face  16   s , the end face  16   s  is processed so that the depth of the swirling groove  16   b  becomes L 2  from L 1 , however the circular flat face  16   r  on the outside of the swirling groove  16   b  is formed into the same flat face as the bottom face of the swirling groove  16   b . Thereby the height H 1  and the height H 2  are measured, and the difference between H 1  and H 2  becomes the depth of the swirling groove  16   b.    
   Therefore, when the difference between H 1  and H 2  becomes L 2 , processing the end face  16   s  is finished, the depth of the swirling groove  16   b  can become L 2 . 
   In the present invention, the circular flat face  16   r  formed into the same flat face as the flat part  16   b   1  of the swirling groove  16   b  is formed on the end face  16   s  side in which the swirling groove  16   b  is formed, and on the outer circumference side above the swirling groove  16   b . Thereby it is possible to measure the depth of the swirling groove  16   b  by the difference between the height H 1  of the circular flat face  16   r  and the height H 2  of the end face  16   s , furthermore it is possible to measure H 1  and H 2  while processing. 
   Since the swirler  16  according to the present invention is processed as mentioned above, it is possible to manufacture elaborate products by processing for a short time. In measuring the height H 1  and H 2 , it is desirable to use a height gauge  22  or a laser height instrumentation as shown in  FIG. 9 . Furthermore it is desirable that the swirler  16  is formed by sintering or cold forging. 
   According to the present embodiment as mentioned above, it is possible to manufacture a fuel injection valve by processing for a short time, therefore it is possible to manufacture a fuel injection valve at a low cost. Furthermore it is possible to restrain dispersion of the depth of the swirling groove  16   b , thereby it is possible to mount a fuel injection valve which hardly generates dispersion of spray on an engine, and it is possible to restrain deterioration of emission of the engine.