Patent Publication Number: US-2016237969-A1

Title: Fuel Injection Valve

Description:
TECHNICAL FIELD 
     The present invention relates to a fuel injection valve for use in an internal combustion engine for an automobile. 
     BACKGROUND ART 
     In internal combustion engines for automobiles, for example, an electromagnetic fuel injection valve driven by an electric signal from an engine control unit is widely used. 
     Fuel injection valves of this kind include those called a port injection type attached to an intake pipe for indirectly injecting fuel into a combustion chamber, and those called a direct injection type for directly injecting fuel into the combustion chamber. 
     In the latter direct injection type valves, a spray shape to be formed by the injected fuel determines combustion performance. Thus, it is necessary to optimize the spray shape in order to obtain a desired combustion performance. Here, the optimization of the spray shape can also be rephrased as spray direction and penetration. 
     Known as a fuel injection valve is one including a valve element provided movably, a drive means for driving the valve element, a valve seat which the valve element moves toward and away from, and a plurality of orifices provided downstream of the valve seat (see PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL: JP 2009-30572 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     It is known that a spray to be ejected from a fuel injection valve is ejected nearly in an axial direction where an injection hole is machined. Like the fuel injection valve described in PTL 1, for a fuel injection valve of a type with a plurality of injection holes (orifices), it is required to increase machining accuracy in a direction of each injection hole. It is also required to control a penetration of the spray to be ejected from each injection hole to be shortened in order to avoid interference with a size of an inside of a combustion chamber, a shape of a piston surface, and a valve for air control (inlet valve and exhaust valve) as much as possible for reducing generation of exhaust as components (such as soot, an unburned gas component, in particular). 
     In the fuel injection valve described in PTL 1, the spray penetrations at the injection holes are not taken into consideration. As a method for controlling the spray penetration at each injection hole, it is possible to change diameters of the injection holes. Generally, the spray penetration at each injection hole can be controlled by setting a hole diameter size larger at an injection hole for lengthening the spray penetration and smaller at an injection hole for shortening the spray penetration. 
     However, in a case where the hole diameters of the injection holes are changed, it is necessary to prepare a plurality of tools for machining the hole diameter in accordance with each injection hole and carry out machining using different tools for each injection hole. This also leads to higher costs of manufacturing the fuel injection valves. 
     In order to use different tools in machining the injection holes, it is necessary to change the tools or move a material for forming the injection holes to other machining device. Therefore, a relative position deviation may be caused between the tools and the material, and machining accuracy of injection holes may decline. 
     An object of the present invention is to provide a fuel injection valve that can suppress fuel adhesion to the inside of the combustion chamber and the piston by controlling the penetration of the spray to be ejected from the injection hole, and that can improve exhausting performance (particularly suppression of unburned components). 
     Solution to Problem 
     The object of the present invention can be achieved by, as an example, shortening a penetration of a spray to be ejected from a first injection hole, among a plurality of injection holes, set on a central axis with a center of a connector portion as an axis as well as controlling penetrations of sprays to be ejected from other injection holes. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide a fuel injection valve that can suppress fuel adhesion to an inside of a combustion chamber and a piston by controlling a penetration of a spray to be ejected from each injection hole, and that can improve exhausting performance (particularly suppression of unburned components). 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       [ FIG. 1 ]  FIG. 1  is a longitudinal sectional view illustrating an overall configuration on of a fuel injection valve according to an embodiment of the present invention. 
       [ FIG. 2 ]  FIG. 2  is top and side views of a guide member. 
       [ FIG. 3 ]  FIG. 3  is a longitudinal sectional view illustrating a vicinity of an orifice cup and a guide member in the related art. 
       [ FIG. 4 ]  FIG. 4  is a sectional view of a line A-A of  FIG. 3 , illustrating a seat portion from upstream. 
       [ FIG. 5 ]  FIG. 5  is a view enlarging a vicinity of the seat portion of  FIG. 4  and illustrating flows into and out of injection holes. 
       [ FIG. 6 ]  FIG. 6  is a cross sectional view of an injection hole  71  of  FIG. 5 . 
       [ FIG. 7 ]  FIG. 7  is a contour diagram of an outlet portion  81  of the injection hole  71  of  FIG. 5 . 
       [ FIG. 8 ]  FIG. 8  is a cross sectional view of an injection hole  72  of  FIG. 5 . 
       [ FIG. 9 ]  FIG. 9  is a contour diagram of an outlet portion  82  of the injection hole  72  of  FIG. 5 . 
       [ FIG. 10 ]  FIG. 10  is a view enlarging a vicinity of a seat portion with a twist angle and illustrating flows into and out of injection holes according to an embodiment of the present invention. 
       [ FIG. 11 ]  FIG. 11  is top and side views of a guide member illustrating an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the present embodiment, each injection hole is formed such that an inlet thereof is opened at a substantially conical surface with a diameter thereof on an upstream side larger than one on a downstream side. A seat portion contacted by a valve element is provided on the substantially conical surface, and the inlet of the injection hole is formed downstream of the seat portion. Upstream of the seat portion, a member for guiding the valve element is fixed to a cup-shaped member forming the injection hole, and a groove is formed on an outer peripheral surface of the guide member or inside thereof. The groove formed in the guide member has a fixed twist angle to a central axis line of a fuel injection valve. This fuel passage groove may be plurally formed, but may be in any shape as long as twist angles are set nearly equal to one another and the fuel passage shape is set smaller than an upstream passage area and larger than a passage area of the seat portion. This twisted fuel passage twists fuel while the valve element is opened, that is, a swirling component is applied. In order to uniform this swirling component, the twist angles of the fuel passage grooves are set nearly equal to one another and the fuel passage shape is set substantially symmetrical to an axis line of the fuel injection valve. Due to nearly uniform swirling component of a fuel flow, an inflow direction at an injection hole inlet changes with an angle. However, a direction of an injection hole outlet is predetermined. Therefore, a fluid flows toward this direction of the injection hole outlet. Thus, when an angle between the inflow direction at the injection hole inlet and the direction at the injection hole outlet is defined as α (0° to 90°), a flow along an injection hole axis becomes dominant without twists in the fuel flow in a case where α is a small angle. Therefore, a spray to be ejected from the injection hole outlet is ejected along the axial direction and forms a long spray penetration in the direction of the injection hole outlet. However, in a case where the angle α is large, the flow that has flowed into the injection hole is forcibly provided with components with twists. Therefore, flow components perpendicular to the injection hole axis (that is, in-plane flow rate) are likely to increase. An increase in this in-plane flow rate causes the spray to be ejected from the injection hole outlet to have a vector with components perpendicular to the spray along the axial direction and the axis. Therefore, due to the components perpendicular to the axis at the injection hole outlet, the spray is ejected in a direction spreading in the direction perpendicular to the axis, and is likely to spread. Furthermore, a spray speed in a direction of the injection hole axis is relatively slowed down. Therefore, the spray penetration into the direction of the injection hole axis is expected to be shortened. Thus, the spray penetration can be shortened by setting the angle between the injection hole inlet and the direction of the injection hole outlet larger. 
     On the other hand, in a case where the injection hole is set on a central axis with a center of a connector portion as an axis, the angle α may not be set larger than at other injection holes. In this case, the spray penetration is lengthened. Thus, at a second injection hole set adjacent to a first injection hole and at a third injection hole set except the injection holes, nonuniform pitch angles among the holes as well as stronger flows into the second injection hole by a smaller angle α due to a smaller inflow angle of a fluid into the second injection hole can shorten the spray penetration at the first injection hole. 
     The present embodiment will be described below in detail with reference to the drawings. 
       FIG. 1  is a longitudinal sectional view illustrating an overall configuration of a fuel injection valve according to an embodiment of the present invention. The fuel injection valve according to the present embodiment is a fuel injection valve that injects a fuel such as gasoline directly to an engine cylinder (combustion chamber). 
     A fuel injection valve body  1  has a hollow fixed core  2 , yoke  3  serving also as a housing, mover  4 , and nozzle body  5 . The mover  4  includes a movable core  40  and a movable valve element  41 . The fixed core  2 , yoke  3 , and movable core  40  are components of a magnetic circuit. 
     The yoke  3 , nozzle body  5 , and fixed core  2  are connected by welding. There are various types in this connecting manner, but in the present embodiment, the nozzle body  5  and the fixed core  2  are connected by welding with a part of an inner periphery of the nozzle body  5  fitted into a part of an outer periphery of the fixed core  2 . In addition, the nozzle body  5  and the yoke  3  are connected by welding such that a part of an outer periphery of this nozzle body  5  is surrounded by the yoke  3 . An electromagnetic coil  6  is installed inside the yoke  3 . The electromagnetic coil  6  is covered, with seal performance maintained, by the yoke  3 , a resin cover  23 , and a part of the nozzle body  5 . 
     Inside the nozzle body  5 , the mover  4  is installed movably in the axial direction. At a tip of the nozzle body  5 , an orifice cup  7  forming a part of the nozzle body is fixed by welding. The orifice cup  7  has injection holes (orifices)  71  to  76 , which will be described later, and a conical surface  7 A including a seat portion  7 B. 
     Inside the fixed core  2 , a spring  8  that presses the mover  4  against the seat portion  7 B, and an adjustor  9  and a filter  10  that adjust a spring force of this spring  8 . 
     Inside the nozzle body  5  and the orifice cup  7 , a guide member  12  that guides movement of the mover  4  in the axial direction is installed. The guide member  12  is fixed to the orifice cup  7 . A guide member  11  that guides the movement of the mover  4  in the axial direction near the movable core  40  is installed. The mover  4  is guided in the movement in the axial direction by the guide members  11  and  12  vertically arranged. 
     The valve element (valve rod)  41  according to the present embodiment is illustrated as a needle type with a tapered tip, but may be a type with a spherical body at the tip. 
     A fuel passage in the fuel injection valve includes an inside of the fixed core  2 , a plurality of holes  13  provided in the movable core  40 , a plurality of holes  14  provided in the guide member  11 , an inside of the nozzle body  5 , a plurality of side grooves  15  provided in the guide member  12 , and the conical surface  7 A including the seat portion  7 B. 
     The resin cover  23  is provided with a connector portion  23 A that supplies excitation current (pulse current) to the electromagnetic coil  6 , and a part of a lead terminal  18  insulated by the resin cover  23  is positioned in the connector portion  23 A. 
     Excitation of the electromagnetic coil  6  housed in the yoke  3  by an external driving circuit (not illustrated) via this lead terminal  18  causes the fixed core  2 , yoke  3 , and movable core  40  to form a magnetic circuit, and the mover  4  to be magnetically attracted against the force of the spring  8  toward the fixed core  2 . At this time, the valve element  41  is opened separated from the seat portion  7 B, and a fuel in the fuel injection valve body  1 , boosted in advance (1 MPa or higher) by an external high pressure pump (not illustrated), is injected from the injection holes  71  to  76 . 
     Turning off the excitation of the electromagnetic coil  6  causes the valve element  41  to be closed, pressed toward the seat portion  7 B by the force of the spring  8 . Here, a main fuel passage from the guide member  12  into the injection holes  71  to  75  through the seat portion  7 B will be described. When a fluid flows downstream from the guide member  12 , the flow is divided into a small space AA to be formed by the guide member  12  and the movable valve element  41 , and a plurality of side grooves  15  provided in the guide member  12 . However, an area of the space AA is far smaller than one to be formed by the side grooves  15 , and the flow of the fluid concentrates in the side grooves  15 . Therefore, the flow passing through each side groove  15 , seat portion  7 B, and injection holes  71  to  75  is called a main fuel passage. As illustrated in  FIG. 2 , the side groove  15  of the guide member  12  forms the fuel passage so as to be in a direction parallel to a fuel injection valve axis O 1 . Therefore, after the fuel passes through the side groove  15 , the fluid contracts with a decrease in a passage area toward the seat portion  7 B, but a flow vector passes in a direction along the conical surface of the orifice cup  7  and in nearly the same direction as the fuel injection valve axis O 1 . An A-A section of  FIG. 3  is illustrated in  FIG. 4 . The orifice cup  7  is illustrated, viewed from an upstream side and excluding the valve element  41  so a to show the seat portion  7 B. Flows of the fluid near this seat portion  7 B are illustrated in  FIG. 5 . As described above, the flows proceed in nearly the same direction as the conical surface and the fuel injection valve axis O 1 . Therefore, in passing through the seat portion  7 B, the fluid flows nearly radially from outside of the conical surface toward a center of the fuel injection valve. Inflow arrows  101  to  105  into the injection holes  71  to  75  face substantially in a central axial direction of the fuel injection valve. Here,  FIG. 5  indicates inlets of the injection holes  71  to  75  with solid lines  81  to  85 , outlets thereof with dotted lines  91  to  95 , and directions of the injection hole outlets with arrows  201  to  205 . An axis line passing through a center of the injection hole inlet  81  and the injection hole outlet  91  is O 101 . Similarly, a central axis line of each injection hole is O 102 , O 103 , O 104 , and O 105 . A flow inside the injection hole  71  on a plane passing through the axis line O 103  and the fuel injection valve axis line O 1  is illustrated in  FIG. 6 . A flow on a plane perpendicular to the axis line O 103  and passing through the inject on hole outlet  93  is illustrated in  FIG. 7 . At an injection hole  73 , the inflow direction  103  and the outlet direction  203  are nearly the same. Therefore, a speed component in a direction of the axis line O 103  in  FIG. 6  is large. Thus, the fluid from the injection hole outlet  93  is ejected with a fast speed component in a direction of a vertical axis. On the other hand, at the injection hole  71 , the angle α (α; 0° to 90°) between the inflow direction  101  and the outlet direction  201  is applied This angle α generates the twist effect in the fluid inside the injection hole. This twist shows that a speed in a direction of a plane component perpendicular to the direction of the axis line O 101  (hereinafter cal led in-plane flow rate) is applied. This application of the in-plane flow rate reduces the speed in the direction of the axis line O 101 , when the fluid is ejected from the injection hole outlet  81 , and the fluid proceeds in the direction of the plane perpendicular to the axis line O 101 , that is, in a spreading direction. A flow inside the injection hole  71  on a plane passing through the axis line O 101  and the fuel injection valve axis line O 1  is illustrated in  FIG. 8 . A flow on a plane perpendicular to the axis line O 101  and passing through the injection hole outlet  91  is illustrated in  FIG. 9 . Shown below is an embodiment according to the present invention that in a case where the twist angle α cannot be actively applied at the injection hole  73 , the flow flowing into the injection hole  73  is suppressed by arrangement of other injection holes. 
     As illustrated in  FIG. 10 , the angle α may not be set larger at the injection hole  73  than at other injection holes. In this case, the spray penetration is lengthened. Thus, at injection holes  72  and  74  set adjacent to the injection hole  73  and at injection holes  71  and  75  set adjacent otherwise, nonuniform pitch angles β 1  and β 2  among the holes as well as stronger flows into the injection holes  72  and  74  by a smaller angle α due to a smaller inflow angle β 1  of a fluid into the injection holes  72  and  74  can shorten the spray penetration at the injection hole  73 . On the other hand, it is possible to shorten the spray penetration by making the angle α larger by 
     setting the inflow angle β 2  of the fluid at the injection holes  71  and  75  illustrated in  FIG. 10  larger than the inflow angle β 1  of the fluid into the injection holes  72  and  74 . A flow on a plane perpendicular to the axis line of each injection hole and passing through the injection hole outlet is indicated in  FIG. 11 . Comparison of the drawings on the right and left sides of  FIG. 11  shows that the speed component in a direction of the axis line O 103  is suppressed at the injection hole  73 . This is because the inflow angle β 1  of the fluid into the injection holes  72  and  74  is set smaller and the flows into the injection holes  72  and  74  are strengthened. 
     REFERENCE SIGNS LIST 
       1  fuel injection valve body 
       2  hollow core 
       3  yoke 
       4  mover 
       5  nozzle body 
       6  electromagnetic coil 
       7  orifice cup 
       8  spring 
       9  adjustor 
       10  filter 
       11  guide 
       12  guide member (PR guide) 
       13  fuel passage (anchor) 
       14  fuel passage (rod guide) 
       15  side groove (PR guide) 
       18  lead terminal 
       23  resin cover 
       23 A connector portion 
       40  movable core 
       41  movable valve element 
       71  to  75  injection hole 
       7 A conical surface 
       7 B valve seat portion 
       81  to  85  injection hole inlet 
       91  to  95  injection hole outlet 
       101  to  105  injection hole inflow direction by a conventional guide member 
       201  to  205  direction of injection hole outlet 
     O 1  central axis of fuel injection valve 
     O 101  to O 105  central axis of injection hole