Patent Publication Number: US-2011073682-A1

Title: Fuel Injection Valve

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese application serial no. 2009-219894, filed on Sep. 25, 2009, the contents of which are hereby incorporated by references into this application. 
     FIELD OF THE INVENTION 
     The present invention relates to a fuel injection valve for an internal combustion engine, and in particular, relates to a structure thereof for suppressing variation of fuel injection amount due to deformation of a spring used therefor. 
     BACKGROUND OF THE INVENTION 
     Conventionally, in an internal combustion engine of vehicles such as for automobiles, a solenoid type fuel injection valve that is driven by an electric signal from an engine control unit has been used generally. 
     Such conventionally known fuel injection valve is constituted in such a manner that a solenoid and a yoke are disposed around a cylindrical stator core, the lower portion of the yoke accommodating the solenoid is provided with a nozzle casing in which a movable core including a valve element is disposed. The valve element is applied with a spring force of a valve return spring via the movable core toward a valve seat side (refer to JP-A-10-339240). 
     When energizing the solenoid, a magnetic circuit is formed routing from the yoke through the stationary core, the movable core and the nozzle element to the yoke, the movable core with the valve element is magnetically attracted to the stationary core side so as to make a gap between the valve element and the valve seat, and thereby fuel is injected through a nozzle hole. 
     In the above referred to fuel injection valve, by adjusting an entire length of the spring (valve return spring) exerting on the movable core by means of a spring force adjusting member (it&#39;s also called as a adjuster), the spring force can be changed to thereby change the valve operation time and as a result, the fuel flow rate characteristic of injection can be adjusted to a desired value. A coil spring although is used generally as the valve return spring, torsion torque (torsion stress) is apt to occur in the coil spring when adjusting the spring by compressing the spring with the adjuster. When the adjuster is press fitted at the time of adjusting, the spring is deformed by means of this torsion torque, thereby, a resistance to the fuel flow in the fuel passage where the spring is disposed varies and variation of the fuel flow rate characteristic in the injector may result therefrom. Further, in the fuel injector in which the spring contacts to the movable core including the valve element, there are occasions when the torsion torque is suddenly released by an impact from the movable core caused during the movable valve element is actuated. Thereby, the spring restores to its original state, as a result of this, the fuel flow rate characteristic may vary. 
     Further, when the inner side or the outer side of the spring is not guided at its both ends, the deformation of the spring becomes much remarkable. 
     Incidentally, a fuel injection valve which injects fuel directly into a cylinder for an internal combustion engine is widely diffused recently. In such a direct injection type fuel injection valve, in view of freedom of attachment thereof, a so-called long nozzle type injector as shown in  FIG. 7  has been proposed. The so-called long nozzle type injector has a nozzle casing  105  which is provided at the lower portion of the yoke  104  and whose diameter is reduced and whose length is prolonged. 
     In such a so-called long nozzle type injector, by the prolonged nozzle (long slender) component thereof, the valve element  108  is also reduced in the diameter thereof and prolonged in the length thereof. Such a long slender valve element is comprised of a solid rod for mechanical strength thereof and the solid rod having a needle valve or a ball valve at the top end thereof. 
     As shown by an arrow in  FIG. 7 , a flow direction of fuel passing through the inner side of a spring  112  is changed at the end of the spring by the valve element  108  so that the fuel is guided through gaps between coil portions of the spring  112  to a fuel passage provided around the outer surface of the valve element  108 . Accordingly, when the spring  112  is compressed by an adjuster  113  at the time of adjusting the fuel flow rate characteristic, since the gaps between coil portions of the spring  112  are narrowed, the fuel flow rate characteristic is reduced. 
     When the fuel flow rate characteristic varies or reduces in the above manner, such may cause adverse effects to the engine performance, exhaust gas performance and/or the like. 
     SUMMARY OF THE INVENTION 
     The present invention is to provide a fuel injection valve (injector) capable of suppressing variation or reduction of the fuel flow rate characteristic due to deformation of the spring thereof. 
     (1) In order to achieve the above object, in a fuel injection valve comprising a valve return spring and an adjuster for the valve return spring, the present invention is characterized basically in that parts supporting respectively both ends of the spring in the axial direction are rotatable in the circumferential direction of the spring. Thereby, the generation of torsion torque is suppressed in the spring, and the variation and reduction of the injection fuel flow rate characteristic can be prevented. 
     (2) In the above (1), preferably, each of the parts supporting respectively both ends of the spring have fit portions that rotatably fit to a part of an inner radius or an outer radius of the spring. Thereby, since an effect of suppressing a spring deformation such due to torsion stress can be obtained, the variation and reduction of the fuel flow rate characteristic can be prevented. 
     (3) In the above (1), preferably, one of the parts supporting respectively both ends of the spring contacts to an end portion of the spring at the upstream side with respect to a flow of fuel, and the one is provided with a passage for guiding fuel to the outer radius of the spring. Thereby, a reduction of the fuel injection flow rate can be prevented at the time when adjusting the fuel flow rate characteristic. 
     (4) In the above (1), preferably, one of the parts supporting respectively both ends of the spring is provided with a hole to be a part of a fuel passage and a filter for trapping foreign matter contained in fuel passing through the one of the parts to prevent the foreign matter from flowing into the inside of the fuel injection valve. 
     According to the present invention, it is possible to suppress variation or reduction of the fuel flow rate characteristic due to deformation of the spring thereof, the present invention can enhance the engine performance and exhaust gas performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross sectional view showing an entire constitution of a fuel injection valve representing an embodiment according to the present invention. 
         FIG. 2  is a diagram showing injection fuel flow rate characteristics. 
         FIG. 3  is a vertical cross sectional view showing a major constitution of a fuel injection valve representing another embodiment according to the present invention. 
         FIG. 4  is a vertical cross sectional view showing a major constitution of a fuel injection valve representing still another embodiment according to the present invention. 
         FIG. 5  is a vertical cross sectional view showing a major constitution of a fuel injection valve representing a further embodiment according to the present invention. 
         FIG. 6  is a vertical cross sectional view showing a major constitution of a fuel injection valve representing a still further embodiment according to the present invention. 
         FIG. 7  is a vertical cross sectional view showing an entire constitution of a conventional fuel injection valve and the fuel passage thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be explained with reference to the embodiments shown in the drawings. 
       FIG. 1  is a vertical cross sectional view showing an entire constitution of a fuel injection valve (hereafter it&#39;s called as injector) representing an embodiment according to the present invention. A injector  201  of the present embodiment is the one so-called as a top feed type in which fuel flows into the upper portion of the injector-main body at the time of valve open, after that, flows through in an axial direction of the injector and is injected from nozzle holes  211 B provided at the lower end of the injection valve. The injector  201  is the one that directly inject fuel such as gasoline into a cylinder (combustion chamber) of an engine. 
     The injector  201  includes an cylindrical stationary core  202 , a movable core  203 , a yoke  204  serving also as a injection parts-housing and a nozzle casing (it&#39;s also called as a nozzle holder)  205 . The stationary core  202 , the movable core  203 , the yoke  204  and a solenoid  206  are of components for a magnetic circuit. The solenoid  206  constitutes an actuator for actuating the movable core together with the valve element. 
     The stationary core  202 , the yoke  204  and the nozzle casing  205  are connected to each other by welding. Although there are varieties of connection manners therefor, in the present embodiment, the stationary core  202  and the nozzle casing  204  are connected by welding under a manner where a part of the inner side of the nozzle casing  205  is fitted to a part of the outer side of the stationary core  202 . Further, the nozzle casing  205  and the yoke  204  are connected by welding so as to surround a part of the outer side of the nozzle casing  205  with the yoke  204 . The solenoid  206  is assembled inside the yoke  204 . The solenoid  206  is covered by parts of the yoke  204 , a resin body  207  and the nozzle casing  205  while keeping sealing ability. 
     Inside the nozzle casing  205 , the movable core  203  and a rod shaped valve element  208  connected to the movable core  203  by welding are assembled in a manner to be movable in the axial direction of the nozzle casing. In the present embodiment, a needle type valve element whose top end is tapered is shown as the rod shaped valve element  208 . Instead of it, a type of valve element provided with a ball body at the top end thereof can also be used. Further, although the rod shaped valve element  208  of the present embodiment is shown as connected to the movable core  203  by welding, instead of it, it may be used as the following separate type valve element in which the movable core and the valve element are merely contacted to each other with engagement without welding. In the type where the rod shaped valve element  208  and the movable core  203  are separated, a spring (not shown in Figs.) other than a valve return spring  212  is provided between a guide member  209  for the valve element  208  and the movable core  203  so as to engage the movable core  203  to the valve element  208  by applying the spring force thereof toward the stationary core  202  (in the opposite direction of the force of the valve return spring  212 ) with the force weaker than that of the spring  212 . 
     Inside of the nozzle casing  205  is provided with an upper guide members  209  and a lower guide member  210  that are spaced in a vertical direction so as to guide movably the movable core  203  and the rod shaped valve element  208  in an axial direction of the nozzle casing. 
     The end of the nozzle casing  205  is provided with a nozzle top  211  which is fixed by welding, and constitutes a part of the nozzle casing  205 . The nozzle top  211  is provided with a conical face  211 A including a valve seat portion and a plurality of nozzle holes (orifices)  211 B. 
     Inside of the stationary core  202  is provided with a valve return spring  212  that presses the movable core  203  and the rod shaped valve element  208  toward the valve seat portion of the conical face  211 A, an adjuster  213  that adjusts the force of the spring  212  and a filter  214  having filtering function. 
     Further, a rotatable member  215  being shaped like a ring plate, a sleeve or the like with a hole to be a part of a fuel passage is interposed between the spring  212  and the adjuster  213 . Since a slight gap is provided between the outer diameter of the rotatable member  215  and the inner diameter of the stationary core  202 , the rotatable member  215  is permitted to rotate in an inner circumferential direction of the stationary core  202  (in other words, in a circumferential direction of the spring  212 ). In addition, the movable core  203  with the valve element  208  is also rotatably provided in the nozzle casing  205  in the inner circumference direction of the nozzle casing  205  (in other words, in the circumference of the spring  212 ). 
     When opening the injector, the fuel passage in the injector is constituted by the inside of the stationary core  202  including the adjuster  213  and the rotatable member  215 , plural through holes  203 A provided in the movable core  203 , plural through holes  209 A provided in the guide member  210 , a ring-shaped gap between the conical face  211 A containing the valve seat portion and the tip of the valve element  208 , and plural nozzle holes (multi-holes)  211 B. 
     The outer side of the stator core  201 A is covered by a resin body  207  being provided with a connector portion  207 A that feeds energizing current (pulse current) to the solenoid  206 , and a part of lead terminal  216  insulated by the resin body  207 . The part of the lead terminal  216  is positioned in the connector portion  207 A. 
     When the solenoid  206  accommodated in the yoke  204  is energized by an external driving circuit (not shown) via the lead terminal  216 , a magnetic circuit is formed by the stationary core  202 , the movable core  203  and the yoke  204 , and the movable core  203  is magnetically attracted toward the stationary core  202  against the force of the spring  212 . At this moment, the rod shaped valve element  208  moves away from the valve seat of the conical face  211 A to thereby make the valve open state. Thereby, fuel that is pressurized (to more than 10 MPa) within the injector main body in advance by an external high pressure fuel pump (not shown) is injected via the multi-injection holes  211 B. 
     When the energization to the solenoid  206  is turned OFF, the valve element  208  is pressed onto the seat portion of the conical face  211 A by the force of the spring  212  to thereby make the valve closed state. 
     By controlling the energization time to the solenoid  206  depending on the operating conditions of the engine, the injection fuel flow rate can be controlled corresponding to the operating conditions of the engine. 
       FIG. 2  shows fuel flow rate characteristics representing relationships between the solenoid energization time and injection fuel flow rate. For the fuel injector  201  of the present embodiment, the adjustment work is performed by adjusting the force of the spring  212  (namely the amount of compression of the spring  212 ) by adjusting the position of the adjuster  213  so that the fuel flow rate characteristic matches with that registered in advance in a control unit (not shown) for controlling the engine. 
     When the spring  212  is of a coil spring, the coil spring is apt to generate a torsion torque in the spring  212  when adjusting the force of the spring  212  by adjusting the amount of spring compression in the axial direction with the adjuster  213 . However, according to the present embodiment, since the movable core  203  and the valve element  208  to which one end of the spring  212  contacts and the rotatable member  215  to which the other end of the spring  212  contacts are rotatable in the inner circumferential direction of the nozzle casing  205  (in other words, in the circumferential direction of the spring  212 ), the torsion torque can be canceled out with rotational displacement of both rotatable parts (namely the rotatable member  215  and the movable core  203  with the valve element  208 ). 
     Therefore, the present embodiment can prevent such variation of the injection fuel flow rate characteristic that are caused by variation of the flow passage resistance because of variation of gaps where the fuel passes due to the deformation of the spring  212 , and can enhance engine performance and exhaust gas performance. 
     Now, constitutions of fuel injectors representing other embodiments according to the present invention will be explained by making use of  FIGS. 3 ,  4 ,  5  and  6 . Further, the same reference numerals in the drawings as those in  FIG. 1  show the same parts as those in  FIG. 1 . 
       FIG. 3  is a vertical cross sectional view showing a major constitution of a fuel injector representing another embodiment according to the present invention. A rotatable member  415  corresponds to the rotatable member  215  of  FIG. 1 . Since the rotatable member  415  like a sleeve shape has a slight gap between the outer diameter of the rotatable member  415  and the inner diameter of the stationary core  202 , the rotatable member  415  is rotatable in the inner circumferential direction of the stationary core  202 . 
     Additionally the rotatable member  415  is provided with a recess portion  415 A at a bottom thereof. The inner radius of the recess portion  415 A is slightly larger than the outer radius of the spring  212 . Thereby, a part of the outer radius of one end side of the spring  212  fits into the recess portion  415 A. In addition, a part  208 A of the upper side of the valve element  208  protrudes toward the spring  212 . The outer radius of the upward protruding part  208 A is slightly smaller than the inner radius of the spring  212 , and thereby the protruding part  208 A fits into the inner radius of the spring  212 . In other words, the parts ( 415 ,  208 ) supporting respectively both ends of the spring  212  have fit portions that rotatably fit to a part of an inner radius or an outer radius of the spring. Therefore, the spring  212  is prevented from being deformed and is positioned at the center of the inner diameter of the stationary core  202 , and the fuel flow is stabilized. 
       FIG. 4  is a vertical cross sectional view showing a major constitution of a fuel injector representing still another embodiment according to the present invention. A rotatable member  515  corresponds to the rotatable member  215  of  FIG. 1 . Since the rotatable member  515  like a sleeve shape has a slight gap between the outer diameter of the rotatable member  515  and the inner diameter of the stationary core  202  too, the rotatable member  515  is rotatable in the inner circumferential direction of the stationary core  202 . 
     Additionally the rotatable member  515  is provided with a downward protruding portion  515 A with a part of the fuel passage toward the spring  212  at a bottom thereof. The outer radius of the protruding portion  515 A is slightly smaller than the inner radius of the spring  212 . Thereby, a part of the inner radius of one end side of the spring  212  fits into the protruding portion  515 A. In addition, as well as the other embodiments of  FIGS. 1 and 3 , a part  208 A of the upper side of the valve element  208  protrudes toward the spring  212  and the protruding part  208 A fits to the inner radius of the spring  212 . Therefore, the spring  212  is prevented from being deformed and is positioned at the center of the inner diameter of the stationary core  202 , and the fuel flow is stabilized. 
       FIG. 5  is a vertical cross sectional view showing a major constitution of a fuel injector representing a further embodiment according to the present invention. A rotatable member  615  corresponds to the rotatable member  215  of  FIG. 1 . Since the rotatable member  615  like a sleeve shape has a slight gap between the outer diameter of the rotatable member  615  and the inner diameter of the stationary core  202  too, the rotatable member  615  is rotatable in the inner circumferential direction of the stationary core  202 . 
     Additionally, the rotatable member  615  includes a downward protruding portion  615 A which protrudes toward the spring  212  at the bottom thereof. The outer radius of the protruding portion  615 A is slightly smaller than the inner radius of the spring  212 . Thereby, a part of the inner radius of one end side of the spring  212  fits to the protruding portion  615 A. In addition, as well as the other embodiments of  FIGS. 1   3 , and, a part  208 A of the upper side of the valve element  208  protrudes toward the spring  212  and the protruding part  208 A fits into the inner radius of the spring  212 . 
     Therefore, the spring  212  is prevented from being deformed and is positioned at the center of the inner diameter of the stationary core  202 , and the fuel flow is stabilized. 
     Furthermore, in the present embodiment, a center hole (to be a part of the fuel passage) of the rotatable member  615  is closed at the downstream end by the protruding portion  615 A. In addition, the rotatable member  615  is provided with plural of radial grooves extending from the inner circumference to the outer circumference thereof at just upstream from the protruding portion  615 A. Thereby, the fuel flow is leaded to a gap between the inner radius of the stationary core  202  and the outer radius of the spring  212  instead of being leaded to inner radius side of the spring  212 . Accordingly, since no fuel flows through the gaps between coils of the spring  212 , the flow rate thereof is further stabilized. 
       FIG. 6  is a vertical cross sectional view showing a major constitution of a fuel injector representing a still further embodiment according to the present invention. A rotatable member  715  corresponds to the rotatable member  215  of  FIG. 1 . The present invention has a same structure of the embodiment of  FIG. 1  other than the following technical matter. That is, the rotatable member  715  is provided with a filter  715 A in the inner radius side (hole) of thereof to be a part of the fuel passage. Thereby, foreign matter (primarily, metals, high polymer compounds and the like) can be trapped to prevent the foreign matter from flowing into the inside of the fuel injection valve. As a result, a possible risk of seat defect due to biting of the foreign matter can be avoided. 
     Incidentally, when the flow passage area of the fuel passage in the rotatable members  215 ,  415 ,  515 ,  615  and  715  is decreased extremely in comparison with the flow passage area at the upstream of them, an influence of fuel pressure ripple caused when pressurized (to more than 10 MPa) in advance at the external high pressure fuel pump (not shown) is eliminated, and the variation of the fuel injection amount can be suppressed. 
     Further, in the explanation hitherto, although the fuel injector of in cylinder injection type has been referred to, the present invention is also applicable to a fuel injector that is disposed in an air intake passage.