Patent Publication Number: US-11022084-B2

Title: Vehicle fuel injector

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims under 35 U.S.C. § 119(a) the benefit of Korean Patent Application No. 10-2019-0090454, filed on Jul. 25, 2019, the entire contents of which are incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a gasoline direct injection (GDI) type fuel injector, more specifically, to a vehicle fuel injector having a nozzle in which an outward flow path and a multi-hole type discharge flow path are mixed. 
     2. Description of the Related Art 
     As emission regulations are tightened worldwide, technical developments have been achieved to improve fuel economy and achieve low pollutant emissions. 
     A carbon dioxide (CO 2 ) reduction technology, which is one of these technical developments, includes a technology for reducing a fuel consumption amount of a gasoline engine, that is, technology for reducing a pump loss, improving combustion efficiency, reducing a mechanical loss, and the like. 
     Recently, with the development of next-generation gasoline engine combustion technology that allows drastic reductions in a fuel consumption rate, there is a trend toward development of a lean-burn direct injection engine. 
     Existing multi-hole type nozzles have high injection targeting performance but suffer from a long injection reach distance resulting in wall wetting fuel streams on cylinder liners/piston heads when fuel is injected into combustion chambers. 
     In addition, the multi-hole type nozzle may generate fine dust such as particulate matters (PMs), particle numbers (PNs), and nitrogen oxide (NOx) according to emission standards. 
     Meanwhile, an outward type nozzle is capable of easily being opened or closed using a relatively small force with the aid of oil pressure when a needle is opened, and fuel is injected in a jar shape so that an injection reach distance is short and there is an advantage of generating a mixture. 
     However, the outward type nozzle has problems in that it is difficult to perform correct targeting due to a shape of a combustion chamber, and it is difficult to generate eddy kinetic energy using a fuel jet. 
     As a result, in a case in which it is difficult to generate a uniform mixture and a wall wetting fuel stream occurs in all the above described nozzles, a knocking phenomenon may be generated due to occurrence of local combustion, and exhaust emissions, such as fine dust, may also be generated. 
     SUMMARY 
     The present disclosure is directed to reducing a wall wetting fuel stream phenomenon in a combustion chamber using a nozzle in which an outward flow path and a multi-hole type discharge flow path are mixed to reduce exhaust emissions and prevent a knocking phenomenon. 
     The technical objectives of the present disclosure are not limited to the above, and other objectives may become apparent to those of ordinary skill in the art based on the following description. 
     A vehicle fuel injector according to one embodiment of the present disclosure is provided for injecting a high-pressure vehicle fuel received from a fuel rail into a combustion chamber. 
     The vehicle fuel injector includes a nozzle which includes a plurality of discharge flow paths which are disposed to be spaced apart from each other in a circumferential direction and pass through the nozzle in a longitudinal direction, and outward flow paths formed on an inner circumferential surface of the nozzle, the nozzle having a hollow shape, and a needle bar which is formed to pass through the inner circumferential surface of the nozzle and vertically reciprocally moves on the inner circumferential surface of the nozzle, wherein rotation of the needle bar is adjusted in a left or right direction so that the nozzle is opened or closed. 
     The nozzle may include a guide protrusion formed to protrude from the inner circumferential surface of the nozzle, the needle bar may include a guide groove corresponding to the guide protrusion on an outer circumferential surface of the needle bar, and the guide groove may be concavely formed to be inclined in a downward direction and adjust a rotation angle of the needle bar. 
     The guide groove may include a vertical groove having a vertical section on the outer circumferential surface of the needle bar, and an inclined groove formed to extend from the vertical groove and inclined in a left or right direction with respect to the vertical groove. 
     In the nozzle, choking may occur in the discharge flow path so that fuel is injected at a constant speed. 
     The needle bar may rotate such that the nozzle enters an open state while moving downward, and the needle bar may rotate such that the nozzle enters a closed state while moving upward. 
     A plurality of blades may be formed to protrude in a width direction on a lower end of the needle bar 
     The blade may include a pair of fins formed to protrude from an upper end surface of the blade and spaced apart from each other to form an acute angle therebetween. 
     The pair of fins may provide a discharge path of one of the outward flow paths on the blade in an open state of the nozzle and atomize an injected fuel. 
     The pair of fins may be formed to be detachably attached to an upper end surface of the blade. A tilting groove provided for adjusting installation angles of the fins may be formed on the upper end surface of the blade. 
     The blade may be formed to be inclined downward, and a lower end portion thereof has a tapered shape. 
     A guide member which surrounds and supports a circumference of the needle bar to stabilize movement of the needle bar may be formed at a lower end of the inner circumferential surface of the nozzle. 
     The guide member may be formed to protrude inward at a position corresponding to the discharge flow path in a width direction, and the outward flow paths may be formed at both ends of the guide member in the circumferential direction. 
     A ring guide which surrounds and supports a circumference of the needle bar to stabilize movement of the needle bar may be formed on an upper end of the inner circumferential surface of the nozzle. 
     The ring guide may be formed to have a hollow shape of which an inner circumferential surface surrounds the circumference of the needle bar and include a plurality of discharge holes having a concentric circle. 
     The vehicle fuel injector may further include an armature surrounding an upper circumference of the needle bar, a magnetic core positioned under the armature and disposed around the needle bar, and an elastic member provided between the armature and the magnetic core. 
     The armature may move downward in a direction toward the magnetic core due to a magnetic field generated in a solenoid coil, and the needle bar may move vertically in conjunction with the armature. 
     A non-magnetic body may be provided at a partial section between the armature and the solenoid coil. 
     A stopper disposed above the armature and a position ring disposed under the armature may be formed on the upper circumference of the needle bar, and the stopper and the position ring may be formed to be spaced apart from each other to restrict a movement range of the armature. 
     When a magnetic force is not applied to the armature, the armature may move upward due to the elastic member. 
     A vehicle fuel injector according to another embodiment of the present disclosure includes a nozzle which includes a plurality of discharge flow paths which are disposed to be spaced apart from each other in a circumferential direction and pass through the nozzle in a longitudinal direction, and outward flow paths formed on an inner circumferential surface of the nozzle, the nozzle having a hollow shape, a needle bar which is formed to pass through the inner circumferential surface of the nozzle and vertically reciprocally moves on the inner circumferential surface of the nozzle, wherein rotation of the needle bar is adjusted in a left or right direction so that the nozzle is opened or closed, and a piezo actuator connected to an upper end of the needle bar to control movement of the needle bar. 
     The vehicle fuel injector may include a fixing plate which surrounds an upper circumference of the needle bar, and an elastic member which is provided between the fixing plate and an upper end of the nozzle and provides an elastic force. 
     A ring guide which surrounds and supports a circumference of the needle bar to stabilize movement of the needle bar may be formed on an upper end of the inner circumferential surface of the nozzle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will become more apparent to those of ordinary skill in the art by describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which: 
         FIG. 1  is a conceptual view illustrating a vehicle fuel injector according to one embodiment of the present disclosure; 
         FIG. 2  is a cross-sectional view taken along line A-A′ shown in  FIG. 1 ; 
         FIG. 3A  is a set of partial cross-sectional views illustrating area B shown in  FIG. 2 ; 
         FIG. 3B  is a cross-sectional view taken along line B-B′ shown in  FIG. 3A , 
         FIGS. 4A and 4B  are sets of views illustrating a nozzle and a lower end of a needle bar in order to describe an open state and a closed state of the vehicle fuel injector according to one embodiment of the present disclosure; 
         FIGS. 5A and 5B  are sets of views illustrating a detailed structure of the nozzle operating in conjunction with the needle bar in the vehicle fuel injector according to one embodiment of the present disclosure; 
         FIGS. 6A to 6C and 7A to 7B  are sets of views illustrating a structure which discharges fuel injected through a multi-hole type discharge flow path and an outward flow path in the vehicle fuel injector according to one embodiment of the present disclosure; 
         FIGS. 8A to 8E  are sets of views illustrating operation mechanisms of the vehicle fuel injector according to one embodiment of the present disclosure; 
         FIGS. 9A and 9B  are schematic cross-sectional views of a vehicle fuel injector according to another embodiment of the present disclosure; and 
         FIG. 10  is a schematic cross-sectional view of a vehicle fuel injector and coupling relationships between components of the vehicle fuel injector according to still another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Throughout the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, the terms “unit”, “-er”, “-or”, and “module” described in the specification mean units for processing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof. 
     Further, the control logic of the present disclosure may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller or the like. Examples of computer readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
     Advantages and features of the present disclosure and methods of achieving the same will be clearly understood through embodiments described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments to be disclosed below but may be implemented in various different forms. The embodiments are provided in order to fully explain the present disclosure and fully explain the scope of the present disclosure for those skilled in the art. The scope of the present disclosure is defined by the appended claims. Meanwhile, the terms used herein are provided only to describe the embodiments of the present disclosure and not for purposes of limitation. 
     Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a conceptual view illustrating a vehicle fuel injector according to one embodiment of the present disclosure. 
     Referring to  FIG. 1 , a vehicle fuel injector  100  is a device provided for injecting a high-pressure vehicle fuel supplied through a fuel rail  10  into a combustion chamber (not shown). 
     That is, the vehicle fuel injector  100  receives an electrical signal from an electronic control unit (ECU) and injects the high-pressure fuel into the combustion chamber of a gasoline direct injection (GDI) engine. 
     To this end, the vehicle fuel injector  100  is coupled to the fuel rail  10  and connected to a high-pressure sensor  20  and a wire harness  30  and receives power from an external power source to operate. In this case, an airtight member (O-ring) may be provided on an upper end of a portion at which the vehicle fuel injector  100  is coupled. 
     The vehicle fuel injector  100  injects a correct amount of fuel into the combustion chamber at an appropriate time. 
     Generally, fuel in a liquid state is atomized, mixed with air to form a mixture, and introduced into the combustion chamber during an intake stroke of an engine (not shown), and such a mixture generation process is an important factor to define a combustion phenomenon of a cylinder (not shown). 
     Entire processes of vaporization, mixing with air, and ignition and combustion of the fuel are almost simultaneously performed. 
     An objective of forming the mixture is that the vaporized fuel self-ignites as soon as possible, and the injected fuel is completely burnt while avoiding a high peak-combustion temperature. 
     When the two basic conditions are satisfied, combustion may be performed in which a level of harmful emissions is low while avoiding excessive pressure rise, high combustion noise, and a mechanical/thermal load. 
     To this end, the vehicle fuel injector  100  according to one embodiment of the present disclosure uses a nozzle in which an outward flow path and a multi-hole type discharge flow path are mixed. Therefore, the vehicle fuel injector  100  according to the present disclosure can inject fuel to a suitable injection reach distance and improve injection targeting performance. Detailed explanations will be described below. 
       FIG. 2  is a cross-sectional view taken along line A-A′ shown in  FIG. 1 . 
     Referring to  FIG. 2 , basically, the vehicle fuel injector  100  receives an electrical signal using an electromagnet, and a needle bar  120  vertically moves on an inner circumferential surface of a nozzle  110  to open or close an output side of the nozzle  110 . 
     The vehicle fuel injector  100  according to the present disclosure includes components included in a conventional GDI type fuel injection system with a high-pressure pump (not shown) which constantly compresses fuel and the fuel rail  10  (see  FIG. 1 ) which stores the compressed fuel and through which the compressed fuel is supplied to the vehicle fuel injector  100 . 
     The vehicle fuel injector  100  mainly includes a filter  101 , a support tube  102 , the nozzle  110 , the needle bar  120 , an armature  130 , a magnetic core  140 , an elastic member  150 , and a solenoid coil  160 . 
     In this case, the above-described components are provided for injecting a vehicle fuel and have mechanisms operating in conjunction with each other. 
     Before the components of the present disclosure are described in detail, a structure in which the needle bar  120  moves vertically and rotates and the related components for operating the needle bar  120  will be described. 
     However, the vehicle fuel injector  100  according to the present disclosure injects a vehicle fuel into the combustion chamber and has the same structure as the conventional vehicle fuel injector except for specific features thereof. Accordingly, in the specification, differences of the present disclosure from a conventional fuel injector will be described in detail. 
     The nozzle  110  is provided for injecting a vehicle fuel and preferably has a hollow shape. The nozzle  110  preferably includes a plurality of discharge flow paths  111  and a plurality of outward flow paths  112 . 
     The discharge flow paths  111  are disposed at intervals in a circumferential direction of the nozzle  110 . The discharge flow paths  111  are formed to pass through the nozzle  110  in a longitudinal direction thereof and formed as a plurality of holes. 
     The outward flow paths  112  are formed on the inner circumferential surface of the nozzle  110 . The outward flow paths  112  may be easily opened or closed with a relatively small force with the help of hydraulic pressure. 
     In addition, fuel is injected into the combustion chamber to have a jar shape through the outward flow paths  112 . Accordingly, when the outward flow paths  112  are used, an injection reach distance is short and a risk of generating a wall wetting fuel stream is low so that it is advantageous for forming a mixture. 
     A general multi-hole type flow path is advantageous for injection targeting because of a long injection reach distance. However, due to the advantage, there is a high possibility of generating a wall wetting fuel stream because the injection reach distance is relatively long. 
     In order to solve such a problem, the multi-hole type discharge flow paths  111  and the outward flow paths  112  are simultaneously applied to the nozzle  110  in the present disclosure. 
     The injection reach distance of fuel injected into the combustion chamber through the discharge flow paths is shortened by injecting the fuel into the combustion chamber through the outward flow paths  112 . This reduced injection reach distance is because a pressure is distributed by the fuel injected through the outward flow paths  112 . 
     Accordingly, the injection reach distance of the fuel passing through the discharge flow paths  111  is decreased due to the pressure distribution of the fuel injected through the outward flow paths  112 , and thus the present disclosure may prevent generation of the wall wetting fuel stream. That is, the nozzle  110  may maintain the targeting performance of the discharge flow paths  111  and also prevent the generation of the wall wetting fuel stream. 
     The needle bar  120  is provided as a structure passing through the inner circumferential surface of the nozzle  110 . The needle bar  120  vertically moves on the inner circumferential surface of the nozzle  110 , and rotation thereof is adjusted in a left or right direction so that the nozzle  110  is opened or closed. 
     As the needle bar  120  moves downward, the needle bar  120  rotates in an open state, and as the needle bar  120  moves upward, the needle bar  120  rotates in a closed state. 
     Next, components provided for operating the needle bar  120  operating in conjunction with the nozzle  110  will be described. 
     First, the armature  130  surrounds an upper circumference of the needle bar  120 . The armature  130  has a function for electrical-mechanical energy converting, circuit opening or closing, and the like through rotation or movement. 
     The armature  130  moves downward in a direction toward the magnetic core  140  due to a magnetic field generated in the solenoid coil  160 . In this case, the needle bar  120  is vertically moved in conjunction with the armature  130 . 
     In this case, non-magnetic bodies  103  are provided in some sections between the armature  130  and the solenoid coil  160  to focus a magnetic density thereof. 
     The non-magnetic bodies  103  are inserted into the support tube  102  positioned between the filter  101  and the nozzle  110 . 
     The magnetic core  140  is positioned under the armature  130  and disposed around the needle bar  120 . 
     The elastic member  150  is a spring which provides an elastic force and is disposed between the armature  130  and the magnetic core  140 . 
     When the armature  130  receives an electrical signal from an external device and moves downward, the elastic member  150  is folded until the armature  130  comes into contact with the magnetic core  140 . 
     Next, when the armature  130  does not receive the electrical signal, the elastic member  150  moves the armature  130  to an upper portion which is an original position (initial position) using an elastic restoring force. 
     A stopper  170  and a position ring  180  are disposed to be spaced apart from each other on the upper circumference of the needle bar  120 . 
     The stopper  170  is positioned at an upper end of the needle bar  120  and positioned above the armature  130 . The armature  130  is prevented from moving upward due to an installation position of the stopper  170 . 
     The position ring  180  is disposed under the armature  130 . The armature  130  is prevented from moving downward due to the installation position of the position ring  180 . 
     In other words, the stopper  170  and the position ring  180  restrict a vertical movement distance d of the armature  130  so that the armature  130  moves only between the stopper  170  and the position ring  180 . 
       FIG. 3A  is a set of partial cross-sectional views illustrating area B shown in  FIG. 2 ;  FIG. 3B  is a cross-sectional view taken along line B-B′ shown in  FIG. 3A ; and  FIGS. 4A and 4B  are sets of views illustrating the nozzle and a lower end of the needle bar in order to describe an open state and a closed state of the vehicle fuel injector according to one embodiment of the present disclosure; 
     Referring to  FIGS. 3A and 3B , a guide protrusion  113  is formed to protrude from the inner circumferential surface of the nozzle  110 . A guide groove  121  corresponding to the guide protrusion  113  is formed in an outer circumferential surface of the needle bar  120 . 
     In this case, as shown in  FIG. 3B , the guide groove  121  is concavely formed to be inclined in a downward direction and adjusts a rotation angle of the needle bar  120 . 
     The guide groove  121  includes a vertical groove  121   a  and an inclined groove  121   b.    
     The vertical groove  121   a  is formed as a vertical section in the outer circumferential surface of the needle bar  120 . 
     The inclined groove  121   b  is formed to extend from the vertical groove  121   a . The inclined groove  121   b  has a structure inclined in the left or right direction with respect to the vertical groove  121   a.    
     Rotation of the nozzle  110  and rotation of the needle bar  120  are adjusted by the guide protrusion  113  and the guide groove  121  which operate in conjunction with each other. Rotation of the lower end of the needle bar  120  is adjusted to open or close the nozzle  110 . 
     In  FIG. 4A , the closed state of a lower end of the nozzle  110  is maintained by the needle bar  120 . In this case, a plurality of blades  122  is formed to protrude from the lower end of the needle bar  120  in a width direction. 
     The blades  122  are concentric with the inner circumferential surface of the nozzle  110  and rotate to open or close the nozzle  110 . 
     In  FIG. 4B , rotation of the needle bar  120  is adjusted such that the lower end of the nozzle  110  enters an open state. As described above, when rotation of the blades  122  of the needle bar  120  is adjusted, the discharge flow path  111 , which is one of discharge paths of the nozzle  110 , can be opened or closed. 
       FIGS. 5A and 5B  are sets of views illustrating a detailed structure of the nozzle operating in conjunction with the needle bar in the vehicle fuel injector according to one embodiment of the present disclosure. 
     Referring to  FIGS. 5A and 5B , in the nozzle  110 , the multi-hole type discharge flow paths  111 , the outward flow paths  112 , and guide members  114  are integrally formed. 
     In this case, the guide members  114  surround and support a circumference of the needle bar  120  to stabilize movement of the needle bar  120 . The guide members  114  are disposed on a lower end of the inner circumferential surface of the nozzle  110 . 
     The guide members  114  are formed to protrude inward at positions corresponding to the discharge flow paths  111  in the width direction. The outward flow paths  112  are formed at both ends of the guide members  114  in the circumferential direction. 
       FIGS. 6A to 6C and 7A to 7B  are sets of views illustrating a structure which discharges fuel injected through the multi-hole type discharge flow path and the outward flow path in the vehicle fuel injector according to one embodiment of the present disclosure. 
     Referring to  FIGS. 6A to 6C and 7A to 7B , a blade (of the plurality of blades)  122  is provided as a structure being inclined downward, and a lower end portion thereof has a tapered shape. 
     The nozzle  110  includes flow path grooves  124  at portions close to the blades  122 . A vehicle fuel passing through the discharge flow paths  111  and the outward flow paths  112  is injected to the outside through the flow path grooves  124 . 
     In this case, the blade  122  includes a pair of fins  123  formed to protrude from an upper end surface thereof and spaced apart from each other to form an acute angle therebetween. 
     The pair of fins  123  may provide discharge paths of the outward flow path  112  in an open state of the blade  122  to atomize the injected fuel. 
     In  FIG. 6C , when the needle bar  120  opens the nozzle  110 , the discharge flow paths  111  and the outward flow paths  112  (see  FIGS. 5A and 5B ) are simultaneously opened. 
     Accordingly, the vehicle fuel injected through the discharge flow paths  111  is injected in a state in which a pressure is lower than that of the conventional multi-hole type nozzle. 
     Accordingly, a conventional problem of a wall wetting fuel stream in a combustion chamber occurring due to a short injection reach distance of a vehicle fuel can be prevented. In addition, the discharge flow paths  111  may maintain injection targeting. 
     In other words, cavitation occurs in a vehicle fuel injected through the discharge flow paths  111  which are relatively high-pressure areas on the discharge flow paths  111  so that a velocity of flow is fixed due to choking. 
     The cavitation occurs due to an internal pressure difference in the discharge flow path  111 . The discharge flow path  111  normally operates in a movement area of the cavitation so that an injection speed of the vehicle fuel is fixed. 
     Referring to  FIG. 7A , the pair of fins  123  formed on the upper end surface of the blade  122  are spaced apart from each other to form the acute angle. 
     Accordingly, the pair of fins  123  prevent an injection overlap phenomenon of the vehicle fuel injected through the outward flow path  112  (see  FIGS. 5A and 5B ). 
     When the nozzle  110  (see  FIGS. 6A to 6C ) enters an open state due to rotation of the needle bar  120 , the pair of fins  123  atomize the vehicle fuel injected through the outward flow path  112  (see  FIGS. 5A and 5B ) in each direction to facilitate fission of an initial droplet. 
     The pair of fins  123  may also be formed to be detachably attached to the upper end surface of the blade  122 . 
     In this case, tilting grooves (not shown) provided for adjusting installation angles of the fins  123  may be formed on the upper end surface of the blade  122 . 
     Accordingly, when the angle between the fins  123  is changed according to a shape of the combustion chamber, mist of the vehicle fuel may be distributed slightly more to an area in which a tumble flow is strong. 
     That is, when the angle between the fins  123  can be adjusted, an injection amount of the vehicle fuel can be adjusted. Meanwhile, as shown in  FIG. 7B , airtight portions  125  are provided at both ends of the blades  122  of the needle bar  120 . 
       FIGS. 8A to 8E  are sets of views illustrating operation mechanisms of the vehicle fuel injector according to one embodiment of the present disclosure. 
     Referring to  FIGS. 8A to 8E , the vehicle fuel injector  100  operates according to steps a, b, c, d, and e. 
     The step a is a pre-operation step in which the armature  130  restricted by the stopper  170  receives a force from the elastic member  150  in an upward direction. As a result, when the armature  130  is in contact with the stopper  170 , airtightness between the nozzle  110  and the needle bar  120  is maintained. 
     In the step b, the needle bar  120  of the vehicle fuel injector  100  in which an induced magnetic force is generated moves downward so that the nozzle  110  enters an initial open state. 
     In this case, when an electrical signal is applied to the vehicle fuel injector  100  in which the induced magnetic force is generated due to the solenoid coil  160 , the armature  130  moves toward the magnetic core  140  and collide with the position ring  180 . Next, the armature  130  moves downward with the needle bar  120  until the elastic member  150  is compressed. 
     In this case, the needle bar  120  reciprocally and vertically moves on the inner circumferential surface of the nozzle  110  in conjunction with the nozzle  110 , and rotation thereof is adjusted in the left or right direction. Accordingly, the needle bar  120  opens or closes the nozzle  110 . 
     In the step c, when the needle bar  120  moves downward, a lower end portion of the nozzle  110  is opened as rotation of the needle bar  120  is adjusted in conjunction with the nozzle  110 . Accordingly, the discharge flow path  111  and the outward flow path are simultaneously opened so that the vehicle fuel is injected. 
     In the step d, when the electrical signal is not applied to the armature  130 , the magnetic force is removed, and the armature  130  is moved upward by the elastic member  150 . In this case, the armature  130  returns to an initial position at which the armature  130  is in contact with the stopper  170  like the step e. 
     In the state in which the armature  130  is in contact with the stopper  170 , the needle bar  120  moves upward and rotates in conjunction with the nozzle  110 . 
     Accordingly, the needle bar  120  maintains a state in which the nozzle  110  is closed until the electricity is applied to the armature  130 . 
       FIGS. 9A and 9B  are schematic cross-sectional views of a vehicle fuel injector according to another embodiment of the present disclosure. 
     Referring to  FIGS. 9A and 9B , in a vehicle fuel injector  100  according to another embodiment of the present disclosure, a ring guide  115  is formed on an upper end of an inner circumferential surface of a nozzle  110 . 
     That is, the ring guide  115  which surrounds a circumference of a needle bar  120  to stabilize movement of the needle bar  120  is formed at the upper end of the inner circumferential surface of the nozzle  110 . 
     In this case, the ring guide  115  is formed to have a hollow shape surrounding the circumference of the needle bar  120 . In this case, a guide surface  118  which is an inner circumferential surface of the ring guide  115  is in contact with the needle bar  120 . 
     The ring guide  115  includes a plurality of discharge holes  116  having a concentric circle. The discharge holes  116  are connected to discharge flow paths  111  and outward flow paths of the nozzle  110  to provide discharge paths of a vehicle fuel. 
       FIG. 10  is a schematic cross-sectional view of a vehicle fuel injector and coupling relationships between components of the vehicle fuel injector according to still another embodiment of the present disclosure. 
     Referring to  FIG. 10 , in a vehicle fuel injector  100  according to still another embodiment of the present disclosure, a piezo actuator  200  is used instead of a solenoid coil. 
     The piezo actuator  200  is connected to an upper end of a needle bar  120  and controls movement of the needle bar  120 . 
     A fixing plate  190  and an elastic member  150  are disposed between the piezo actuator  200  and a nozzle  110 . 
     The fixing plate  190  surrounds an upper circumference of the needle bar  120 . 
     The elastic member  150  is provided between the fixing plate  190  and an upper end portion of the nozzle  110  and provides an elastic force. 
     In this case, a ring guide  115  which surrounds a circumference of the needle bar  120  to stabilize movement of the needle bar  120  is formed at an upper end of an inner circumferential surface of the nozzle  110 . 
     According to the present disclosure, fuel can be injected to a suitable injection reach distance and injection targeting performance can be improved using a nozzle in which an outward flow path and a multi-hole type discharge flow path are mixed. 
     Accordingly, the present disclosure can reduce exhaust emissions and prevent a knocking phenomenon by reducing a wall wetting fuel stream phenomenon in a combustion chamber. 
     The present disclosure is not limited to the above-described embodiments and may be variously modified and implemented in a range in which the technical spirit of the present disclosure allows.