Method of producing an electromagnetic fuel injector

Information

  • Patent Grant
  • 4974312
  • Patent Number
    4,974,312
  • Date Filed
    Friday, June 30, 1989
    35 years ago
  • Date Issued
    Tuesday, December 4, 1990
    34 years ago
Abstract
An electromagnetic fuel injector suitable for use in an automotive engine has a cylindrical yoke constituting a body of the fuel injector, a solenoid coil and a stator core fixedly received in the cylindrical yoke, a movable core adapted to be attracted by the stator core, and a movable valve responsive to the movable core so as to be moved into and out of contact with a fuel injection valve seat in accordance with the balance of force between an electromagnetic force produced by the solenoid coil and a force produced by a spring received in the stator core. The stator core is coaxially received in the cylindrical yoke with a portion of the material of either one of the stator core and the yoke being plastically deformed into an annular groove formed in the opposing surface of the other of the stator core and the yoke. In consequence, the stator core and the yoke are coupled to and held on each other by the contracting force produced by the plastically deformed material in and around the annular groove.
Description
Claims
  • 1. A method of producing an electromagnetic fuel injector comprising:
  • disposing a cylindrical yoke having a penetrating hole in a bottom part thereof and a bore communicated with the penetrating hole at a lower end thereof and opened at an upper end thereof concentrically with respect to a cylindrical center guide pin in such a manner that the cylindrical center guide pin is fitted into the penetrating hole of the cylindrical yoke to support the cylindrical yoke;
  • disposing, concentrically with respect to the cylindrical center guide pin, an outer guide around the cylindrical yoke to support an outer periphery of an upper part of the cylindrical yoke;
  • disposing a stator core having a central tube-like portion and a collar portion extended radially outward from a middle part of the central tube-like portion, with the outer periphery of the collar portion having a coupling groove therein concentrically with respect to the cylindrical center guide pin in such a manner that a lower end of the central tube-like portion is supported by the cylindrical center guide pin inserted therein, and the outer periphery of the collar portion where the groove is formed is contacted with a periphery of the bore of the cylindrical yoke; and
  • pressing locally an inner peripheral edge of an upper end of the cylindrical yoke vertically downwardly, while keeping concentricities of the stator core, the cylindrical yoke, the cylindrical center guide pin, and the outer guide, to plastically flow material of the cylindrical yoke into the coupling groove of the collar thereby fixing the cylindrical yoke with the stator core.
  • 2. A method according to claim 1, including a step of producing the coupling groove in the form of an annular groove whose cross-section is W-shaped.
  • 3. A method according to claim 2, including a step of disposing a dielectric bobbin with a coil wound therearound in such a position that a lower end of the central tube-like portion of the stator core is inserted into the bobbin.
  • 4. A method according to claim 1, including a step of disposing a dielectric bobbin with a coil wound therearound in such a position that a lower end of the central tube-like portion of the stator core is inserted into the bobbin.
  • 5. A method according to claim 1, including a step of forming the guide pin to have a plurality of stepped surfaces so that peripheral surfaces of the guide pin ensure the concentricity of the stator core and the cylindrical yoke and that stepped end faces support the yoke against the pressing force.
  • 6. A method according to claim 2, including a step of forming the cylindrical center guide pin to have a plurality of stepped surfaces so that peripheral surfaces of the guide pin ensure the concentricity of the stator core and the cylindrical yoke and the stepped end faces support the yoke against the pressing force.
Priority Claims (1)
Number Date Country Kind
61-255712 Oct 1986 JPX
BACKGROUND OF THE INVENTION

This is a divisional of application Ser. NO. 112,148, filed Oct. 26, 1987, now abandoned. The present invention relates to an electromagnetic fuel injector and a method of producing the same. More particularly, the invention is concerned with an electromagnetic fuel injector suitable for use in automotive engines, and also to a method of producing such a fuel injector Japanese Patent Laid-Open Publication No. 119364/1985, particularly FIG. 1 of the drawings attached thereto, shows a typical known electromagnetic fuel injector. The fuel injector has a movable valve part which is integrally composed of a ball valve 11, a plunger rod 10 and a plunger 7 which serves as a movable core. In operation, an electric current is supplied to a solenoid coil 4 so that a magnetic circuit is formed so as to include the plunger 7, a stator core 2 and a yoke 6 so that a magnetic attracting force is generated to enable the stator core 2 to attract the plunger 7. When the supply of the electric current to the solenoid coil 4 is ceased, the magnetic attracting force is extinguished so that the movable valve part is reset to the original position by the force of the spring 5. Usually, the mechanical connection between the stator 2 and the yoke 6 is attained by caulking by means of a jig which is moved downward onto the brim of an opening in the yoke so as to plastically deform the material of the yoke simultaneously over the entire circumference of the opening in the yoke. This connecting method, however, is disadvantageous in that the center of the caulking force applied to the peripheral region of the connecting portion tends to be deviated from the center of the opening in the yoke, so that a difficulty is encountered in uniformly caulking the yoke. The yoke also tends to be deformed to cause an offset between the axes of the yoke and the stator core in the assembled state. Furthermore, since the precision of the construction of a fuel injector depends on the radial size of the stator core and the length of the surface at which the stator core is coupled to the yoke, the caulking method mentioned above inherently has a possibility of a large eccentricity, resulting in a large fluctuation of the assembly precision in the axial direction which often reaches 0.06 mm (see FIG. 4). In the known fuel injector in which the yoke and the stator are fixed to each other by caulking, it is necessary that a valve guide and a plunger rod guide have large lengths in order to ensure a smooth and precise reciprocating movement of the movable core. The use of such long valve guide and long plunger rod guide inevitably increases the size of the fuel injector and complicates the construction of the same. Accordingly, an object of the present invention is to provide a fuel injector having a high assembly precision, as well as a method of producing the same, thereby overcoming the above-described problems of the prior art. To this end, according to one aspect of the invention, there is provided an electromagnetic fuel injector comprising: a cylindrical yoke constituting a body of the fuel injector; a solenoid coil and a stator core fixedly received in the cylindrical yoke; a movable core adapted to be attracted by the stator core; and a movable valve responsive to the movable core so as to be moved into and out of contact with a fuel injection valve seat in accordance with the balance of force between an electromagnetic force produced by the solenoid coil and a force produced by a spring received in the stator core; wherein the stator core is coaxially received in the cylindrical yoke with portion of the material of either one of the stator core and the yoke being plastically deformed into an annular groove formed in the opposing surface of the other of the stator core and the yoke, whereby the stator core and the yoke are coupled to and held on each other by the contracting force produced by the plastically deformed material in and around the annular groove. According to another aspect of the invention, there is provided a method of producing an electromagnetic fuel injector of the type having a cylindrical yoke constituting a body of the fuel injector, a solenoid coil and a stator core fixedly received in the cylindrical yoke, a movable core adapted to be attracted by the stator core, and a movable valve responsive to the movable core so as to be moved into and out of contact with a fuel injection valve seat in accordance with the balance of force between an electromagnetic force produced by the solenoid coil and a force produced by a spring received in the stator core, the method comprising the steps of: holding the yoke between a center guide and an outer guide such that the inner and outer peripheral surfaces of the yoke are contacted and guided by the center guide and the outer guide, respectively; coaxially placing the stator core in the yoke while guiding the stator core by the center guide; locally pressing the peripheral edge portion of either one of the yoke and the stator core so as to cause a portion of material of the pressed member to plastically flow in a direction substantially perpendicular to the pressing force into an annular groove formed in the opposing surface of the other of the yoke and the stator core, thereby coupling the yoke and the stator core by the contracting force of the plastically deformed material in and around the annular groove. The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiment when the same is read in conjunction with the accompanying drawings.

US Referenced Citations (3)
Number Name Date Kind
4339873 Kanamara et al. Jul 1982
4392296 Kanamara et al. Jul 1983
4564145 Takada et al. Jan 1986
Foreign Referenced Citations (1)
Number Date Country
201878 Sep 1986 JPX
Divisions (1)
Number Date Country
Parent 112148 Oct 1987