Patent Publication Number: US-6669116-B2

Title: Orifice plate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an injector to be used for fuel injection in an engine. More specifically, the present invention relates to an orifice plate disposed at the tip of the injector and used for setting characteristics of fuel injection. 
     2. Description of Related Art 
     An electromagnetic injector conventionally used for fuel injection in an engine is typically provided with a seat part at the tip of a nozzle body to cover a valve body formed at the tip of a needle valve from the tip. This seat part is provided with a fuel passage hole, to the tip of which a thin orifice plate having a plurality of orifices (small pores) is attached. Fuel having passed through the fuel passage hole is injected at a predetermined injection angle through those orifices. 
     Regarding the injector (fuel injection valve) including the above kind of orifice plate, the applicant of the present application has proposed a technique capable of prompting fuel atomization in Japanese patent unexamined publication No. 10-18943. 
     As shown in FIG. 15, the injector disclosed in the above publication includes a valve body  70   a  having a conical shape at the tip of a needle valve  70 . At the tip of a nozzle body  71 , a fuel passage hole  72  is formed. Around the fuel passage hole  72 , there is formed a seat part  71   a  on which the valve body  70   a  is seated for a valve closed time. Two orifice plates  73  and  74  are fixedly superposed one on top of the other at the tip of the nozzle body  71  to cover the fuel passage hole  72  from the front side (the lower side in FIG.  15 ). These orifice plates  73  and  74  are provided with a plurality of orifices  73   a  and  74   a , respectively, punched in positions within the fuel passage hole  72 . These orifices  73   a  and  74   a , as shown in FIG. 16, are formed each having a central axis C 1 , C 2 , C 3 , or C 4  at an angle with a central axis O of the fuel passage hole  72  so that each distance between the axes C 1  and C 2  and between the axes C 3  and C 4  is widened downward. Thus, the orifices  73   a  and  74   a  are formed inclining to be oblique to each surface of the orifice plates  73  and  74 . These orifices  73   a  and  74   a  are arranged in corresponding positions in the two orifice plates  73  and  74  respectively and have an equal inner diameter. The orifices  73   a  and  74   a  being inclined as above have stepped parts  75  on a superposed surface, namely, a joint portion between the orifices  73   a  and  74   a . By this stepped part  75 , the fuel flow passage provided by the orifices  73   a  and  74   a  is narrowed at the joint portion between the orifices  73   a  and  74   a  in a fuel injecting direction. Fuel to be sprayed will therefore impinge upon the stepped parts  75 , so that the flow of fuel becomes turbulent. This turbulent fuel is utilized to prompt atomization of the fuel to be injected. 
     However, the orifice plates  73  and  74  of the conventional injector disclosed in the above publication need manufacturing to have the inclined orifices  73   a  and  74   a , which would make it difficult to machine the plates  73  and  74  with accuracy. This conventional technique, in addition, requires forming of a plurality of orifices  73   a  or  74   a  inclined in different directions in each single orifice plate  73  and  74 , as shown in FIG.  17 . This would increase the number of machining steps due to punching of the orifices  73   a  and  74   a , leading to a problem of productivity. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an orifice plate which can facilitate machining for providing an inclination to fuel to be injected through an orifice. 
     Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     To achieve the purpose of the invention, there is provided an orifice plate which is mounted at a tip of an injector to cover a fuel passage hole formed at the tip, the orifice plate including: a plate body constructed in layers; and an orifice for allowing fuel having passed through the fuel passage hole to be injected; wherein the orifice is constructed of a plurality of holes each formed in each layer of the plate body so that each hole is perpendicular to a surface of the plate body, the holes being disposed in communication with each other and with displacements from each other along a line obliquely intersecting the plate body. 
     According to another aspect of the invention, there is provided an injector provided with the orifice plate described above, wherein the injector includes a plate holder provided with an injection hole, and the orifice plate is fixedly pressed against the tip of the injector by means of the plate holder and the orifice is positioned within the injection hole. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. 
     In the drawings, 
     FIG. 1 is a sectional view of an injector to be used in an engine in a preferred embodiment; 
     FIG. 2 is an enlarged sectional view of a tip part of the injector; 
     FIG. 3 is an enlarged sectional view of one of orifices; 
     FIG. 4 is a plane view of a plate body in an unfolded state; 
     FIG. 5 is a plane view of the plate body in a folded state; 
     FIG. 6 is a front view of the plate body of FIG. 5; 
     FIG. 7 is a plane view of a plate holder, showing a top thereof; 
     FIG. 8 is a sectional view of the plate holder; 
     FIG. 9 is an explanatory view to show how to mount an orifice plate in the plate holder; 
     FIG. 10 is a sectional view of the plate holder on which the orifice plate is mounted; 
     FIG. 11 is a bottom view of the plate holder on which the orifice plate is mounted; 
     FIG. 12 is a modified example of the plate holder of FIG. 11; 
     FIG. 13 is a modified example of the plate holder of FIG. 11; 
     FIG. 14 is a modified example of the plate holder of FIG. 11; 
     FIG. 15 is a sectional view of a tip end of an injector in a prior art; 
     FIG. 16 is an enlarged sectional view of orifice plates in the prior art; and 
     FIG. 17 is a sectional view of one of the plates including an orifice in the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of a preferred embodiment of an orifice plate and an injector using the orifice plate embodying the present invention will now be given referring to the accompanying drawings. 
     FIG. 1 is a longitudinal sectional view of an electromagnetic fuel injection valve (injector)  1  which is used in an engine. This injector  1  is basically provided with a fuel receiving pipe  3  provided in a housing  2 , a solenoid  6  constructed of a conducting wire  4  and a bobbin  5 , a movable core  7  which is vertically movable by magnetization and demagnetization of the solenoid  6 , a needle  8  formed integrally with the movable core  7  and provided with a spherical valve body  8  at the tip thereof, a body  9  surrounding the tip of the needle  8 , and a holder  15  internally holding the movable core  7 , the needle  8 , and the body  9 . 
     The upper end of the fuel receiving pipe  3  forms a connector  10  which is connected to a delivery pipe (not shown). An O-ring  11  is attached around the connector  10 . A filter  12  is fit in the connector  10 . An electrical connector  13  for connection with wiring is integrally formed with the upper part of the housing  2 . A terminal  14  of the electrical connector  13  is connected to the solenoid  6 . 
     An inner pipe  16  is mounted in the fuel receiving pipe  3  and a coil spring  17  is disposed between the inner pipe  16  and the movable core  7 . This coil spring  17  urges the movable core  7  downward to close the valve body  8   a  of the needle  8 . 
     At the lower part of the body  9 , namely, at the tip of the injector  1 , a fuel passage hole  18  is formed. The end of the holder  15  forms a sleeve  19  with this hole  18  centered. An orifice plate  21  mentioned later (see FIG.  2  and other figures) is fixed between the sleeve  19  and the body  9  by means of the plate holder  22 . 
     FIG. 2 shows an enlarged sectional view of the tip of the injector  1 . The periphery of the fuel passage hole  18  being open toward the tip side of the body  9  forms a seat  20  on which the valve body  8   a  is seated for the valve closed time. At the tip of the body  9 , the orifice plate  21  is fixed to cover the fuel passage hole  18  from its front side (lower side in FIG.  2 ). The orifice plate  21  is pressed against the tip of the body  9  and fixed thereto. Specifically, this orifice plate  21  is welded to the body  9  by laser welding. The sleeve  19  is formed extending from the tip of the body  9  to cover the periphery of the plate holder  22 . 
     The orifice plate  21  is constructed of a single plate body  23  (see FIG.  4 ), which will be mentioned later in detail, folded into four layers. This orifice plate  21  is formed with a plurality of orifices  24  for allowing the fuel flowing through the fuel passage hole  18  to be injected. The plate holder  22  includes an injection hole  25  at the center thereof. The orifices  24  of the orifice plate  21  are positioned to be present within the injection hole  25 . This injection hole  25  is disposed in the sleeve  19 . 
     FIG. 3 is an enlarged sectional view of part of the plate body  23 , showing one of the orifices  24 . This orifice  24  is constituted of plural holes (four holes in the present embodiment)  27   a ,  27   b ,  27   c , and  27   d  which are punched or pierced in the plate body  23  so that each hole is perpendicular to the surface of the plate body  23  and are allowed to communicate with one another in a folded state of the plate body  23 . The four holes  27   a  to  27   d  communicating with one another are disposed along a line L 1  obliquely intersecting the plate body  23  with displacements from one another. In this case, the intersecting line L 1  is inclined to the center axis O of the fuel passage hole  18  to widen toward the lower side. In the present embodiment, four lines L 1  obliquely intersecting the plate body  23  in section are provided and, along each line L 1 , plural holes  27   a  to  27   d  are arranged. Accordingly, four orifices  24  are formed extending in different oblique directions. Thus, the injecting directions of the orifices  24  are different from one another as shown in FIG.  2 . It is to be noted that only two of the four orifices  24  are shown in FIG.  2 . In each orifice  24 , the four holes  27   a  to  27   d  are disposed so that their respective centers are displaced outward stepwise from the one nearest the tip of the injector  1  (body  9 ). 
     As shown in FIG. 3, respective centers of the four holes  27   a  to  27   d  forming each orifice  24  deviate gradually in a centrifugal direction. Accordingly, the four holes  27   a  to  27   d  are provided with inner minute steps  28   a  each formed on each superposed surface of the plate body  23 , that is, on a connected portion between the hole  27   a  and the hole  27   b , a connected portion between the hole  27   b  and the hole  27   c , and a connected portion between the hole  27   c  and the hole  27   d . With these inner minute steps  28   a , the inside of the orifice  24  becomes partially narrower in a fuel injecting direction. On the other hand, inner minute steps  28   b  opposite to the steps  28   a  partially widen the inside of the orifice  24  in the fuel injecting direction (indicated by an arrow in FIG.  3 ). 
     FIG. 4 shows a plane view of the plate body  23  in an unfolded state before being folded into a layered state to constitute the orifice plate  21 . The plate body  23  includes two large-diameter disks  23   a  and  23   b  and two small-diameter disks  23   c  and  23   d , which are superposed on top of one another in layers, a plurality of joint parts  23   e  which join adjacent two each among the disks  23   a  to  23   d  and are folded to superpose the disks  23   a  to  23   d , and two projections  23   f  one each provided in the disks  23   a  and  23   d  disposed at both end sides. The plate body  23  is press-molded as a unit from a metal for example SUS  304 . In each disk  23   a ,  23   b ,  23   c , or  23   d , the four holes  27   a ,  27   b ,  27   c , or  27   d  are formed at vertexes of an imaginary square centering on the center of each disk. Those holes  27   a ,  27   b ,  27   c , or  27   d  in each disk  23   a ,  23   b ,  23   c , or  23   d  coordinate with the holes  27   a ,  27   b ,  27   c , or  27   d  correspondingly positioned in other disks. In each joint part  23   e , cutouts  23   g  are provided in both sides thereof to facilitate folding of each joint part  23   e . 
     FIG. 5 shows the plate body  23  in the folded state, namely, a plane view of the orifice plate  21 . FIG. 6 is a front view of the orifice plate  21  of FIG.  5 . The plate body  23  in the folded state is provided with a circumferential stepped part  29  between the large-diameter disks  23   a  and  23   b  and the small-diameter disks  23   c  and  23   d . The folded joint parts  23   e  and the projections  23   f  project outward from the circumferential edges of the disks. The holes  27   a  to  27   d  of the disks  23   a  to  23   d  are disposed on top of one another with displacements from one another. 
     FIG. 7 is a plane view of the plate holder  22 , showing the upper side thereof. FIG. 8 is a sectional view of the plate holder  22 . This plate holder  22  has substantially a upside down cup shape having a small depth (height) with a circular disk shaped bottom wall  22   a  and a peripheral wall  22   b  formed continuous downward (in FIG. 8) from the bottom wall  22   a.  The plate holder  22  includes, on its upper surface in FIG. 8, stepped parts  30  engageable with the outer peripheries of the large-diameter disks  23   a  and  23   b  and the small-diameter disks  23   c  and  23   d  and their stepped parts  29 , and recesses  31  engageable with the folded joint parts  23   e . The plate holder  22  is provided at its center with the injection hole  25  mentioned above. These stepped parts  30  and recesses  31  are made by a method of punching a plate up to half of the thickness thereof (i.e., a half-punching method). 
     For fixing the orifice plate  21  constructed in layers of the folded plate body  23  at the tip of the injector  1  (the body  9 ), the orifice plate  21  is, as shown in FIGS. 9 and 10, fit in the plate holder  22  so that the joint parts  23   e  and the projections  23   f  of the disks  23   a  to  23   d  are engaged in the recesses  31 . FIG. 11 is a view of the plate holder  22  seen from below in a state where the orifice plate  21  is fit as shown FIG.  10 . Inside of the injection hole  25 , the orifices  24  of the orifice plate  21  are disposed without interfering with the plate holder  22 . The plate holder  22  with the orifice plate  21  fit therein is mounted in the sleeve  19 , placed at the tip of the injector  1  (the body  9 ), and laser-welded thereto. Thus, as shown in FIG. 2, the orifice plate  21  is fixedly pressed against the tip of the body  9  by the plate holder  22  and fixedly held therein. 
     The injector  1  in the present embodiment, as described above, is attached to an intake air manifold of an engine. A wire such as a feeder wire, a signal wire, or the like is connected to the electrical connector  13  of the injector  1 . A delivery pipe is connected to the connector  10  for receiving fuel. When the solenoid  6  is magnetized in a state where fuel is supplied from the delivery pipe to the fuel receiving pipe  3  of the injector  1 , the needle  8  as well as the movable core  7  is operated to compress the coil spring  17 , thereby allowing the valve body  8   a  to be separated from the seat  20  into a valve open state. During this valve open time, the fuel is allowed to flow from the fuel receiving pipe  3  to the body  9 , the clearance between the valve body  8   a  and the seat  20 , and the fuel passage hole  18 , and then the fuel is injected through the plural orifices  24 . 
     At this time, the fuel passing through the orifices  24  at a downward inclined angle with respect to a radial direction is injected in the directions spreading out in a substantially pyramid or conical shape. In passing each orifice  24 , the inner steps  28   a  and therefore the flow of fuel becomes turbulent. This turbulent fuel flow prompts atomization of the fuel to be sprayed, so that the fuel becomes easy to burn. 
     In the present embodiment, each orifice  24  in the orifice plate  21  is constructed of the plurality of holes  27   a  to  27   d  each perpendicularly punched in the plate body  23 , which is folded so that the holes  27   a  to  27   d  are disposed in communication with one another and with stepwise displacements with respect to one another along the line L 1  obliquely intersecting the plate body  23 . Accordingly, four lines L 1  obliquely intersecting the plate body  23  are provided extending in different directions and, along each line L 1 , the plurality of holes  27   a  to  27   d  are disposed to constitute each orifice  24 , so that four orifices  24  are provided in different injecting directions. For forming each orifice  24 , the plurality of holes  27   a  to  27   d  have only to be punched in the plate body  23  in a perpendicular direction to the surface of the plate body  23 . These holes  27   a  to  27   d  can be punched in a single punching operation by means of a punching device and the like at the same time when the plate body  23  is press-molded as shown in FIG.  4 . The orifice plate  21  in the present embodiment, specifically, does not need to be machined to punch the holes  27   a  to  27   d  in an oblique direction with respect to the plate body  23 . Thus, the orifice plate  21  can be easily manufactured. In addition, the forming of the plural orifices  24  in different inclined directions does not require to punch the plurality of holes  27   a  to  27   d  individually, which prevents the number of steps of punching from being increased. According to the orifice plate  21  in the present embodiment, therefore, the fuel can be injected through the four orifices  24  respectively in different oblique directions and the machining thereof can be facilitated, resulting in an increased productivity. 
     According to the orifice plate  21  in the present embodiment, the plural holes  27   a  to  27   d  communicated with one another, forming each orifice  24 , are displaced outward stepwise from the one nearest the tip of the injector  1 , namely, the body  9 . Thus, the fuel can be injected through each orifice  24  in an oblique direction to a centrifugal direction. The fuel injected through the four orifices  24  can be radially widened with respect to the central axis O of the fuel passage hole  18 , namely, the central axis of the injector  1 , thereby achieving diffusion of the injected fuel. 
     In the injector  1  in the present embodiment, the orifice plate  21  is held at the tip of the injector  1  (the body  9 ) by the plate holder  22 . Accordingly, as compared with the case where the orifice plate is attached by itself to the tip of the injector, the orifice plate  21  can surely be fixed to the body  9  against the fuel pressure. Furthermore, the fuel injected through the four orifices  24  of the orifice plate  21  passes through the injection hole  25  of the plate holder  22  and is discharged outside the injector  1 . The fuel injected through each orifice  24  can be prevented from being obstructed by the plate holder  22  and therefore the desired injection characteristics, for example, the injecting stream direction and shape through each orifice  24 , can be ensured. 
     According to the injector  1  in the present embodiment, the plate body  23  folded at the joint parts  23   e  is provided with the stepped parts  29  at the outer peripheries of the large-diameter disks  23   a  and  23   b  and the small-diameter disks  23   c  and  23   d  when superposed on top of one another. The orifice plate  21  is fit in the plate holder  22  so that the stepped parts  29  of the orifice plate  21  are engaged in the stepped parts  30  of the plate holder  22 . Thus, the orifice plate  21  can be held in place without rotating. This makes it possible to prevent rotation of the orifice plate  21  even when the pressure of fuel to be injected acts on the plate  21  and change in inclination of fuel to be sprayed through each orifice  24 . As a result, the injecting direction from the orifice plate  21  can be prevented from being changed improperly. Specifically, the direction of fuel to be injected through each orifice  24  of the orifice plate  21  can stably be held. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For instance, the following alternatives can be adopted. 
     In the above embodiment, as shown in FIG. 2, the orifice plate  21  is fixed to the body  9  in the inside of the sleeve  19  disposed at the tip of the injector  1  by means of the orifice plate  21 . An alternative design is to fix the orifice plate  21  to the body  9  by only the plate holder  22  without using the sleeve  19 . Furthermore, the orifice plate  21  may be fixed by itself to the injector (body) without using the plate holder. In any case, the same effects as in the above embodiment can be obtained. 
     In the above embodiment, as shown in FIG. 11, the orifice plate  21  is exposed in an entire area of the injection hole  25  of the plate holder  22 . Alternatively, the plate holder  22  may be constructed to have reinforcing ribs  50  disposed in the injection hole  25  so that the plurality of orifices  24  of the orifice plate  21  are positioned within openings  51  defined by the reinforcing ribs  50  as shown in FIGS. 12 to  14  respectively. In this case, the orifice plate  21  is held by the reinforcing ribs  50  in the injection hole  25  of the plate holder  22 . Therefore, the orifice plate  21  can be prevented from being deformed due to the pressure of fuel at injection and can maintain the stable injection characteristics. 
     In the above embodiment, four orifices  24  are provided in the orifice plate  21  so that each orifice  24  is placed at each vertex of a square. As shown in FIGS. 12 to  14 , alternatively, the number of orifices  24  may be changed to any number other than four and also their respective positions may be changed from the vertexes of the square. 
     Instead of the plurality of orifices  24  in the above embodiment, furthermore, a single orifice  24  may be provided in the orifice plate  21 . 
     In the above embodiment, the plate body  23  constituting the orifice plate  21  is constructed of the disks which are different in diameter, namely, the large-diameter disks  23   a  and  23   b  and the small-diameter disks  23   c  and  23   d . An alternative design is the use of the plate body  23  including disks all of which are equal in diameter. In this case, the joint parts  23   e  and the projections  23   f  described in the above embodiment are formed in an identical shape. 
     The plate body  23  in the above embodiment is constructed of the integrally formed large-diameter disks  23   a  and  23   b , small-diameter disks  23   c  and  23   d , joint parts  23   e , and others, and is folded at the joint parts  23   e  so that the disks  23   a  to  23   d  are superposed on top of one another, thereby forming the orifice plate  21 . Alternatively, the orifice plate  21  may be constituted of large-diameter disks and small-diameter disks which are separately formed and superposed on top of one another. 
     While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.