Abstract:
There is provided a solenoid actuator which is easy to carry out wiring work for coils thereof, and at the same time allows reduction of manufacturing costs through common application of a fixed wiring. A solenoid actuator is supplied with electric power from a power source, for generating an electromagnetic force to drive a driven member such that the driven member performs reciprocating motion. Two electromagnets each have a coil and arranged such that they are opposed to each other and spaced from each other. An armature is connected to the driven member, and arranged between the two electromagnets, for performing reciprocating motion in accordance with energization and deenergization of the two electromagnets to thereby drive the driven member such that the driven member performs the reciprocating motion. Two terminals are connected to opposite ends of said coil of said each of said two electromagnets, and arranged such that the two terminals protrude outward from each of the two electromagnets, respectively. A connector has four metal connectors electrically connectible to the power source. Each two of the metal connectors are connected to the terminals of the each of the two electromagnets, by effecting engagement between the each two of the metal connectors and the two terminals of the each of the two electromagnets in a direction parallel to a direction of the reciprocating motion of the armature.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a solenoid actuator for reciprocatingly driving a driven member by electromagnetic forces of two electromagnets. 
     2. Description of the Prior Art 
     Conventionally, a solenoid actuator of this kind is known which is applied to a valve-actuating mechanism for driving an intake or exhaust valve of an internal combustion engine to open and close the intake or exhaust valve. The valve-actuating mechanism has been proposed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 11-126715, which includes an armature connected to the intake or exhaust valve, and upper and lower electromagnets for vertically attracting the armature. The armature reciprocates between the upper and lower electromagnets whereby the intake or exhaust valve is driven to open or close. Further, in this kind of solenoid actuator which uses two electromagnets, to the coil of each electromagnet, two electric wires, hence a total of four electric wires, are connected from a lateral side, for supplying electric power thereto. 
     However, in the solenoid actuator described above, the valve-actuating mechanism of the internal combustion engine is limited in size, and hence space for wiring is also limited. It is not easy to carry out wiring work for the four electric wires within this limited space, and puts a large burden on workers. Further, the distance between the coils of the two electromagnets varies between a plurality of valve-actuating mechanism different in valve lift amount, which makes it impossible to apply the same electrical wiring to them. This increases the manufacturing costs of the engine. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a solenoid actuator which is easy to carry out wiring work for coils thereof, and at the same time allows reduction of manufacturing costs through common application of a fixed wiring. 
     To attain the above object, the present invention provides a solenoid actuator supplied with electric power from a power source, for generating an electromagnetic force to drive a driven member such that the driven member performs reciprocating motion, comprising: 
     two electromagnets each having a coil and arranged such that the two electromagnets are opposed to each other and spaced from each other; 
     an armature connected to the driven member, and arranged between the two electromagnets, for performing reciprocating motion in accordance with energization and deenergization of the two electromagnets, to thereby drive the driven member such that the driven member performs the reciprocating motion; 
     two first metal connector elements connected to opposite ends of the coil of the each of the two electromagnets, and arranged such that the two first metal connector elements protrude outward from the each of the two electromagnets; and 
     a connector having four second metal connector elements electrically connectible to the power source, each two of the second metal connector elements being connected to the two first metal connector elements of the each of the two electromagnets, by effecting engagement between the each two of the second metal connector elements and the two first metal connector elements of the each of the two electromagnets in a direction parallel to a direction of the reciprocating motion of the armature. 
     According to this solenoid actuator, by effecting engagement between each two of the second metal connector elements of the connector and the two first metal connector elements of each of the two electromagnets, the first metal connector elements and the second metal connector elements corresponding thereto are connected to each other, whereby the coils of the electromagnets became electrically connected to the power source. In this case, the work of providing wiring for the coils of the two electromagnets can be carried out by causing the second metal connector elements of the connector to be engaged with the first metal connector elements of the electromagnets in a direction parallel to the direction of reciprocating motion of the armature, and the work for removing the wiring can be carried out only by effecting the disengagement between the first and second metal connector elements. This makes it possible to carry out the work for providing or removing the wiring even when there is limited space in a direction orthogonal to the direction of reciprocating motion of the armature. Further, since the engaging direction in which the connector is engaged with the electromagnets is parallel to the direction of reciprocating motion of the armature, by properly setting the length of each of the first and second connector metal elements along the engaging direction, and a distance between two pairs each consisting of the each two of the second metal connector elements, it is possible to accommodate variation in the distance between the two electromagnets among different solenoid actuators which are different in stroke of the driven member, whereby the connector of a single kind can be commonly applied to the different solenoid actuators. This makes it possible to reduce the manufacturing costs of the solenoid actuators. In the state of the solenoid actuator having the coils of the two electromagnets connected to the power source, as described above, in accordance with energization and deenergization of the two electromagnets, effected by causing and inhibiting supply of electric power from the power source to the electromagnets, the armature is caused to perform reciprocating motion, whereby the driven member is driven for the reciprocating motion. 
     Preferably, the each of the two electromagnets each includes a bobbin having the coil wound therearound, the two first metal connector elements being terminals arranged on the bobbin, and the connector is in a form of a rectangular column and has one end face, another end face opposite to the one end face, and a cut-away portion formed by cutting away a parallelepiped portion therefrom, the cut-away portion having a wall facing toward and parallel to the another end face, the four second metal connector elements being arranged in two first openings formed in the another end face of the connector and two second openings formed in the wall facing toward the another end face. 
     More preferably, the connector has four third openings formed in the one end face, the third openings having third metal connector elements respectively arranged therein , the third metal connector elements being electrically connected respectively to two of the four second metal connector elements arranged within the two first openings and two of the four second metal connector elements arranged within the two second openings, the third openings receiving terminals of a cable connected to the power source. 
     More preferably, the bobbin has a first brim having an end and a second brim, as well as a terminal portion projecting outward from the end of the first brim, and the terminals arranged on the bobbin projects perpendicularly from the terminal portion. 
    
    
     The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a valve-actuating mechanism of a vehicle engine to which is applied a solenoid actuator according to an embodiment of the present invention; 
     FIG. 2 is a perspective view of the solenoid actuator appearing in FIG. 1; 
     FIG. 3 is an exploded perspective view of FIG. 2 solenoid actuator; 
     FIG. 4A is a perspective view of a core of the solenoid actuator appearing in FIG. 3; 
     FIG. 4B is a sectional view taken on line A—A of FIG. 4A; 
     FIG. 5 is an exploded perspective view of the core shown in FIGS. 4A and 4B; 
     FIG. 6A is a perspective view of a core plate as a component of the core shown in FIGS. 4A and 4B; 
     FIG. 6B is a perspective view showing the opposite side of the FIG. 6A core plate; 
     FIG. 6C is a plan view of the core plate; 
     FIG. 7A is a perspective view of a joint and an armature of the FIG. 2 solenoid actuator; 
     FIG. 7B is a plan view of the joint and the armature of FIG. 7A; 
     FIG. 8A is a perspective view of bobbins each bearing its associated components and a connector of the FIG. 2 solenoid actuator before they are assembled; and 
     FIG. 8B is a perspective view of the bobbins each bearing its associated components and the connector of the FIG. 2 solenoid actuator after they are assembled. 
    
    
     DETAILED DESCRIPTION 
     The invention will now be described in detail with reference to the drawings showing an embodiment thereof. In the embodiment, a solenoid actuator according to the invention is applied to a valve-actuating mechanism of a vehicle engine, not shown, having four valves per cylinder. 
     Referring first to FIG. 1, the valve-actuating mechanism is comprised of a pair of solenoid actuators  1 ,  1  mounted in a cylinder head  2  of the vehicle engine. During operation of the engine, the solenoid actuator  1  arranged on the right-hand side as viewed in the figure drives two intake valves  3 ,  3  as driven members (only one of them is shown in the figure), thereby opening and closing two intake ports  2   a ,  2   a  (only one of them is shown in the figure) of the engine, while the solenoid actuator  1  arranged on the left-hand side as viewed in the figure drives two exhaust valves  4 ,  4  as driven members (only one of them is shown in the figure), thereby opening and closing two exhaust ports  2   b ,  2   b  (only one of them is shown in the figure) of the same. 
     These two solenoid actuators  1 ,  1  are identical in construction to each other, so that the following description will be made by taking the right-hand solenoid actuator  1  for driving the intake valves  3  as an example. Further, for convenience of description, sides indicated by B and B′ of a two-headed arrow B-B′ in FIG. 2 are referred to as the “front” side and the “rear” side, respectively, while sides indicated by C and C′ of a two-headed arrow C-C′ are referred to as the “left” side and the “right” side, respectively. 
     As shown in FIGS. 1 to  3 , the solenoid actuator  1  has its front and rear halves constructed symmetrically to each other in the front-rear direction, and the two intake valves  3 ,  3  are driven by the respective front and rear halves of the solenoid actuator  1 . More specifically, the solenoid actuator  1  includes a casing la (see FIG. 1) mounted in the cylinder head  2 , upper and lower electromagnets  1   b ,  1   b  arranged within the casing la with a predetermined distance therebetween, two armatures  8 ,  8  arranged within a space between the upper and lower electromagnets  1   b ,  1   b  in a vertically slidable manner, two upper coil springs  5 ,  5  (only one of them is shown in FIG. 1) for constantly urging the respective armatures  8 ,  8  downward, and two lower coil springs  6 ,  6  (only one of them is shown in the figure) for constantly urging the respective armatures  8 ,  8  upward. 
     The armatures  8  are rectangular plates each formed of a magnetically soft material (e.g. steel) and having a round through hole  8   a  formed vertically through a center thereof as shown in FIGS. 7A and 7B. Each of the armatures  8  has left and right end faces  8   b ,  8   b  thereof held in contact with armature guides  21  of guide joints  18 , referred to hereinafter. The armature  8  moves vertically in a manner guided by the armature guides  21 . Further, connected to the armature  8  are upper and lower shafts  7 ,  7  which are round in cross section and formed of a non-magnetic austenitic stainless steel. The upper end of the lower shaft  7  and the lower end of the upper shaft  7  are fitted in the round through hole  8   a  of the armature  8 . The armature  8  is supported in a sandwiched manner by flanges  7   a ,  7   a  formed on the upper and lower shafts  7 ,  7  at locations close to the lower and upper ends of the respective upper and lower shafts  7 ,  7 . 
     The lower shaft  7  extends vertically through a guide  12   e  of a central core holder  12 , referred to hereinafter, of the lower electromagnet  1   b , and the lower end of the lower shaft  7  is connected to the upper end of the intake valve  3 . Similarly, the upper shaft  7  extends vertically through a guide  12   e  of a central core holder  12  of the upper electromagnet  1   b . The upper shaft  7  is held in contact with the upper coil spring  5  via a spring-seating member  5   a  mounted on the upper end of the upper shaft  7 . The shafts  7  are guided through the guides  12   e , respectively, whenever the armature  8  moves vertically. The intake valve  3  is held in contact with the lower coil spring  6  via a spring-seating member  6   a  mounted on the upper end of the intake valve  3 . 
     As shown in FIGS. 2 and 3, the upper and lower electromagnets  1   b ,  1   b  are connected to each other via the guide joints  18  referred to hereinafter. The electromagnets  1   b ,  1   b  are identical in construction and arranged in a vertically symmetrical manner with the guide joints  18  interposed therebetween. In the following, description is made by taking the lower electromagnet  1   b  as an example. 
     The lower electromagnet  1   b  includes a core  10  and two coils  16 ,  16  accommodated in respective coil grooves  10   a ,  10   a  formed in the core  10  (see FIG.  3 ). As shown in FIGS. 4A,  4 B and  5 , the core  10  is a unitary assembly formed by combining three core holders, i.e. left and right core holders  11 ,  11  and a central core holder  12 , and left and right laminated stacks  13 ,  13  of core plates  14  by four rods  15 . 
     The left and right core holders  11 ,  11  are each formed of the austenitic stainless steel similarly to the shafts  7 . The two core holders  11 ,  11  are identical in construction and arranged in a manner symmetrically opposed to each other in the left-right direction. The following description is made by taking the left core holder  11  as an example. The left core holder  11  is a unitary comb-shaped member comprised of a base portion  11   a  extending in the front-rear direction and five retainer portions  11   b  each formed to have a shape of a hair comb tooth and extending upward from the base portion  11   a  to a predetermined height in a manner spaced from each other in the front-rear direction. 
     Each of the five retainer portions  11   b  is rectangular in cross section and has a right side face thereof flush with the right side face of the base portion  11   a . On the other hand, the left side face of the middle retainer portion  11   b  protrudes outward or leftward with respect to the left side face of the base portion  11   a , the left side faces of the respective front and rear retainer portions  11   b ,  11   b  are flush with that of the base portion  11   a , and those of the inner retainer portions  11   b ,  11   b  formed between the middle retainer portion  11   b  and the respective front and rear retainer portions  11   b ,  11   b  are slightly recessed inward or rightward from the base portion  11   a . It should be noted that the middle retainer portion  11   b  is formed by integrating a portion protruding outward or leftward from the base portion  11   a.    
     Formed in respective predetermined portions of the base portion  11   a  are four through holes  11   c  each extending in the left-right direction and having a left-side opening chamfered. Further, the front and rear retainer portions  11   b  each have an upper face thereof formed with a round hole  11   e  open upward, and the middle retainer portion  11   b  is formed with a through hole  11   f  extending vertically. 
     The central core holder  12  is also formed of the same austenitic stainless steel as that of the core holder  11 . The central core holder  12  extends in the front-rear direction and has the same length along this direction as that of the core holder  11 . Further, the central core holder  12  has a comb-like shape in side view, which is substantially the same as the shape of the core holder  11 . The central core holder  11  is formed by joining two holder members  12 X,  12 X to each other in the front-rear direction and has opposite flat side faces. Each of the holder members  12 X has an E shape in cross section and has a base portion  12   a  extending in the front-rear direction, and three retainer portions  12   b ,  12   b ,  12   b  integrally formed with the base portion  12   e  and extending upward, respectively, from the front and rear ends and a central portion of the base portion  12   a . The base portion  12   a  is formed therethrough with two through holes  12   c ,  12   c  extending in the left-right direction. The front and rear retainer portions  12   b ,  12   b  are identical in height to the retainer portions  11   b  of the core holder  11 , and the middle retainer portion  12   b  is lower than the other retainer portions  12   b ,  12   b . This enables the upper face of the central retainer portion  12   b  to serve as an indentation for receiving the flange  7   a  of the shaft  7  when the armature  8  is brought into abutment with the core  10  (see FIG.  1 ). 
     Further, the middle retainer portion  12   b  is formed therethrough with a through hole  12   d  extending vertically, in which is fitted the hollow cylindrical guide  12   e  (see FIG. 1) for guiding vertical sliding motion of the shaft  7 . 
     The central core holder  12  is formed by joining the front retainer portion  12   b  of one of the holder members  12 X,  12 X constructed as above to the rear retainer portion  12   b  of the other. The two retainer portions  12   b ,  12   b  joined to each other to form the central portion of the central core holder  12  are opposed to the middle retainer portion  11   b  of the core holder  11 . Similarly, the opposite front and rear retainer portions  12   b ,  12   b  of the central core holder  12  other than the two retainer portions  12   b ,  12   b  forming the central portion are opposed to the front and rear retainer portions  11   b ,  11   b  of the core holder  11 , respectively, while the middle retainer portions  12   b ,  12   b  are opposed to the inner retainer portions  11   b ,  11   b , respectively. Further, the four through holes  12   c  are identical in diameter to the four through holes  11   c  formed through the core holder  11 , respectively, and each opposed to the corresponding one of the four through holes  11   c.    
     The laminated stacks  13  of core plates  14  are each comprised of a pair of laminated stacks  13 X,  13 X of core plates  14  arranged in the front-rear direction. Each laminated stack  13 X is formed by laminates of a predetermined number of core plates  14 , one of which is shown in FIGS. 6A to  6 C, in the left-right direction. Each core plate  14  is formed of a thin non-oriented silicon steel plate and has the whole surface thereof coated with an insulating film  14   d  e.g. of epoxy resin. Adjacent ones of the core plates  14  are insulated from each other by the insulating films  14   d . Further, the core plate  14  is formed to have substantially the same E shape and size as those of the side face of the holder member  12 X, by stamping a non-oriented silicon steel plate. More specifically, the core plate  14  is comprised of a base portion  14   a  extending in the front-rear direction and three magnetic path-forming portions  14   b ,  14   b ,  14   b  extending upward, respectively, from the front and rear ends and central portion of the base portion  14   a , the base portion  14   a  being formed with two through holes  14   c ,  14   c  open in the left-right direction. 
     The three magnetic path-forming portions  14   b  are identical in height to each other, and lower than the front and rear retainer portions  12   b  of the central core holder  12  by a predetermined height (e.g. equal to or smaller than 20 μm), so that an upper face  13   a  of the laminated stack  13 X is lower than the upper face  11   d  of the core holder  11  and an upper face  12   f  of the central core holder  12 . The corresponding through holes  14   c  of the respective core plates  14  are continuous with each other to form a through hole extending through the laminated stack  13 X in the left-right direction. Further, the through holes  14   c  are each identical in diameter to the corresponding through hole  11   c  of the core holder  11  and the corresponding through hole  12   c  of the core holder  12  and positioned in a manner concentric with the corresponding through holes  11   c  and  12   c . Further, the base portion  14   a  is formed with two projections  14   e ,  14   e  at opposite locations slightly laterally outward of the respective through holes  14   c ,  14   c . Each projection  14   e  having a V shape in plan view is projected rightward from the base portion  14   a , and a recess  14   f  is formed in a reverse side of each projection  14   e.    
     The projections  14   e  of one core plate  14  are each fitted in the corresponding recess  14   f  of another core plate  14  adjacent thereto in the rightward direction, whereby the core plates  14  are all held in a closely stacked state. Further, the core plate  14  positioned at the right end of the laminated stack  13 X is formed not with the projections  14   e  and recesses  14   f , but only with horizontally elongated rectangular holes, not shown, in which are fitted the respective corresponding projections  14   e  of the left-hand adjacent core plate  14 . Therefore, the right end face of the laminated stack  13 X is flat, so that it is in intimate contact with the central core holder  12  or the right core holder  11 . 
     Each of the rods  15  is a round bar which is slightly smaller in diameter than the through holes  11   c ,  12   c ,  14   c . The rods  15  are each fitted through the corresponding through holes  11   c ,  12   c ,  14   c  and extend in the left-right direction. The right and left end portions of each rod  15  projecting from the through holes  11   c ,  11   c , respectively, are swaged on the outer end faces of the respective base portions  11   a  of the right and left core holders  11 . Thus, the left-hand laminated stack  13  is sandwiched between the left core holder  11  and the central core holder  12 , while the right-hand laminated stack  13  is sandwiched between the central core holder  12  and the right core holder  11 , whereby these members are rigidly secured to each other to form the core  10 . 
     The coils  16 ,  16  are each formed to have a horizontally elongated annular or toroidal shape and assembled with bobbins  17 ,  17  into a unitary assembly. Each bobbin  17  is formed of a synthetic resin and has a wall U-shaped in cross section for receiving a corresponding one of the coils  16 ,  16  therein. The bobbins  17 ,  17  are accommodated in the two coil grooves  10   a ,  10   a , respectively. Each coil groove  10   a  is defined by the retainer portions  11   b  of the core holders  11 , the retainer portions  12   b  of the central core holder  12 , and the magnetic path-forming portions  14   b  of the core plates  14 . Each of the coils  16 ,  16  is accommodated within the annular coil groove  10   a  in a manner enclosing the members positioned inside the annular coil groove  10   a , i.e. the inner retainer portions  11   b  of the opposite core holders  11 , the middle retainer portion  12   b  of the central core holder  12 , and the middle magnetic path-forming portions  14   b.    
     As shown in FIGS. 8A and 8B, the bobbin  17  is comprised of upper and lower brims  17   a ,  17   a , a terminal portion  17   b  projecting leftward from the left end of the upper brim  17   a , a pair of front and rear terminals (first metal connector elements)  17   b ,  17   c  projecting upward from the terminal portion  17   b , and a pair of V-shaped metal connectors  17   d ,  17   d  connected to the terminals  17   b ,  17   c . The front and rear terminals  17   c ,  17   c  are each formed of an electrically conductive metal plate and arranged such that principal planes thereof are positioned in a manner parallel and opposed to each other in the front-rear direction. The coil  16  is wound around the bobbin  17  between the upper and lower brims  17   a ,  17   a , and the ends of the coil  16  are connected to the metal connectors  17   d ,  17   d , respectively, to be electrically connected to the respective two terminals  17   c ,  17   c.    
     The lower electromagnet  1   b  is constructed as above, and the upper electromagnet  1   b  is identical in construction to the lower electromagnet  1   b . Further, as shown in FIGS. 2,  3  and  7 A,  7 B, the upper and lower electromagnets  1   b ,  1   b  are joined to each other by a pair of left and right guide joints  18 ,  18 . The two guide joints  18 ,  18  are arranged in a manner symmetrically opposed to each other in the left-right direction. Each of the guide joints  18  is formed of an austenitic stainless steel and extends in the front-rear direction such that it has the same length as that of the core holder  11 . The guide joint  18  has substantially the same shape in plan view as that of the core holder  11 . More specifically, the guide joint  18  is comprised of a base portion  18   a  extending in the front-rear direction and a protrusion  18   b  integrally formed with the base portion  18   a  and protruding outward from the central portion of the same. 
     The protrusion  18   b  is formed with a vertical through hole  18   c  which is identical in diameter to the through hole  11   f  of the middle retainer portion  11   b  of the core holder  11  and positioned in a manner concentric with the same. 
     The base portion  18   a  is identical in height to the protrusion  18   b  and has round holes  18   d ,  18   d  formed, respectively, in the opposite end portions of the upper face thereof as well as round holes  18   d ,  18   d  formed, respectively, in the opposite end portions of the lower face thereof. Each round hole  18   d  is identical in diameter and concentric with the corresponding round hole  11   e  of the core holder  11 . Fitted in each of the round holes  18   d  is half of a pin  19  in the form of a round rod formed of an austenitic stainless steel, and the other half of the pin  19  is fitted in the round hole  11   e , whereby the upper and lower cores  10 ,  10  are coupled to each other in a state positioned by the guide joints  18 ,  18 . 
     Further, arranged on the upper face of the base portion  18   a  are front and rear coil-protecting buffer plates  20 ,  20  (see FIG.  3 ). The coil-protecting buffer plates  20 ,  20  are identical in shape to each other and arranged in a symmetrical manner in the front-rear direction, so that the following description will be made by taking the front coil-protecting buffer plate  20  as an example. The front coil-protecting buffer plate  20  is formed of a synthetic resin and smaller in width in the left-right direction than the base portion  18   a . Further, the buffer plate  20  is formed with opposite end projections  20   a  and a central projection  20   b  projecting vertically (downward in this example) from the underside thereof. The base portion  18   a  has two groves  18   e  and a hole  18   g  formed at respective predetermined locations on the front-side portion of the upper face thereof, and the two opposite end projections  20   a  are fitted in the two grooves  18   e , and the central projection  20   b  is fitted in the hole  18   g , respectively, whereby the front coil-protecting buffer plate  20  is mounted on the base portion  18   a . The rear coil-protecting buffer plate  20  is mounted on the base portion  18   a  in the same manner. Further, on the lower face of the base portion  18   a , there are also mounted front and rear coil-protecting buffer plates  20 ,  20  in a similar manner. 
     Further, the four armature guides  21  are fixed to a guide surface  18   g  which is the inner surface of the guide joint  18  at predetermined space intervals, for guiding vertical reciprocating motion of the armatures  8  (see FIGS. 7A,  7 B). Each armature guide  21  is formed of the austenitic stainless steel and has a fitting portion  21   a  which is rectangular in cross section and a guide portion  21   b  continuous with the fitting portion and semicircular in cross section. The guide surface  18   g  has four vertical grooves  18   f  formed at predetermined space intervals. The fitting portion  21   a  of each armature guide  21  is fitted in the corresponding vertical groove  18   f , whereby the armature guide  21  fixed to the guide joint  18 . In this state, each of the guide portions semicircular in cross section protrudes toward the armature  8  from the guide surface  18   g  and at the same time held in contact with the left end face  8   b  or the right end face  8   b  of the armature  8 . Thus, the armatures  8  are each slidably guided by the corresponding ones of the armature guides  21  when they perform vertical reciprocating motion. 
     In a state where the upper and lower electromagnets  1   b ,  1   b  are joined to each other via the guide joints  18  constructed as above, each of the four coils  16  (bobbins  17 ) is vertically sandwiched by the corresponding core  10  and guide joints  18 , as shown in FIG. 2, in a state of the brim  17   a  of the bobbin  17  in abutment with the corresponding coil-protecting buffer plate  20 . The through hole  11   f  of each core  10  and the through hole  18   c  of each guide joint  18  extend vertically in a manner continuous with each other. A bolt, not shown, is screwed into the cylinder head  2  through these holes  11   f ,  18   c , whereby the electromagnets  1   b ,  1   b  are rigidly fixed to the cylinder head  2 . 
     Further, as shown in FIGS. 8A,  8 B, the front (or rear) coil  16  and bobbin  17  of the upper electromagnet  1   b  and the front (or rear) coil  16  and bobbin  17  of the lower electromagnet  1   b  are arranged vertically in an identical position in plan view. The two terminals  17   b ,  17   c  of each of the two bobbins  17  are connected to a connector  22  which is generally in the form of a rectangular column. The connector  22  is formed of a synthetic resin and extends vertically. 
     The connector  22  has an upper end face thereof formed with four upper socket openings  22   a  each in the form of a slit and open upward, and a lower end face thereof formed with two lower socket openings  22   b ,  22   b  each identical in shape to the upper socket opening  22   a . The two lower socket openings  22   b ,  22   b  are parallel and opposed to each other in the front-rear direction and open downward at respective locations corresponding to the terminals  17   b ,  17   c . Further, formed in the lower end portion of the connector  22  is a cut-away portion  22   d  formed by cutting away a parallelepiped portion of the connector  22  from the front side of the same. The cut-away portion  22   d  has an upper wall thereof formed with two middle socket openings  22   c ,  22   c . The middle socket openings  22   c ,  22   c  are open downward and identical in position in plan view to the respective lower socket openings  22   b ,  22   b . Within each of the socket openings  22   b  to  22   c , there is provided a metal connector (second metal connector element)  22   e  comprised of two electrically conductive metal strips arranged in a manner each extending vertically and combined such that root portions thereof are held in contact with each other and a space therebetween is increased toward the outer or forward ends thereof. The terminals  17   c  are each sandwiched by the metal strips of a corresponding one of the metal connectors  22   e  in the socket openings  22   b ,  22   c . Further, a metal connector  22   k  (third metal connector element) similar to the metal connector  22   e  is also arranged within each of the upper socket openings  22   a.    
     The metal connectors  22   k  of the front two of the four upper socket openings  22   a  are electrically connected to the respective metal connectors  22   k ,  22   k  of the middle socket openings  22   c ,  22   c , while the metal connectors  22   k ,  22   k  of the rear two of the four upper socket openings  22   a  are electrically connected to the respective metal connectors  22   e ,  22   e  of the lower socket openings  22   b ,  22   b . Further, a cable, not shown, having four terminals extends from a controller (power source), not shown, and the four terminals of the cable are plugged into the four socket openings  22   a , respectively, whereby the four coils  16  are electrically connected to the controller. 
     Next, the work for mounting and removing the connector  22  of the solenoid actuator  1  constructed as above to the electromagnets  1   b ,  1   b  is described. First, when the connector  22  is mounted to the upper and lower electromagnets  1   b ,  1   b , the lower socket openings  22   b  and the middle socket openings  22   c  of the connector  22  are moved to respective locations over the terminals  17   c  of the upper and lower electromagnets. Then, the connector  22  is moved downward to cause the lower socket openings  22   b  and the middle socket openings  22   c  to be fitted on the respective terminals  17   c . This causes the metal connectors  22   e ,  22   e  within the socket openings  22   b ,  22   c  to hold the terminals  17   c  of the upper and lower electromagnets, respectively, whereby the metal connectors  22   e ,  22   e  are connected to the terminals  17   b ,  17   c  of the upper and lower electromagnets, which connects the coils  16  of the electromagnets  1   b  to the controller. Further, when the connector  22  is removed from the upper and lower electromagnets  1   b ,  1   b , inversely to the above, it is only required to pull the connector  22  upward. 
     As described above, the wiring work for the coils  16 ,  16  of the upper and lower electromagnets  1   b ,  1   b  can be carried out only by fitting the metal connectors  22   e ,  22   e  of the connector  22  on the terminals  17   c ,  17   c  of the upper and lower electromagnets from above. Therefore, even when the space leftward of the electromagnet  1   b  is limited, the wiring work is easy. Further, the direction of connection of the connector  22  is parallel to the direction of reciprocating motion of the armature  8 . Therefore, by properly setting the vertical length of the cut-away portion  22   d , i.e. distance between upper and lower walls thereof, the length of each metal connector  22   e , and the length of each terminal  17   c , it is possible to accommodate variation in the vertical distance between the upper and lower electromagnets  1   b ,  1   b  among valve actuators  1  different in the valve lift amount of the intake valve  3 , such that each metal connector  22   e  can be connected to a terminal  17   c  corresponding thereto. This permits a single type of connector  22  to be commonly to applied electrical wiring to the oils  16 ,  16 , which contributes to reduction of manufacturing costs of the solenoid actuator. 
     In the above embodiment, the connector  22  is connected to the coils  16  by fitting the metal connectors  22   e  within the socket openings  22   b ,  22   c  of the connector  22  on the terminals  17   c  provided on the bobbins  17  of the electromagnets  1   b . The construction for connecting the connector  22  to the coils  16  is not limited to this, but any construction is possible so long as it permits the connection between the connector  22  and the coils  16  to be effected by engagement from above. For instance, terminals may be provided on the connector  22  and socket openings containing the metal connectors may be provided in the bobbin  17 . 
     Further, although the solenoid actuator  1  is applied to the valve-actuating mechanism of the vehicle engine, this is not limitative, but the solenoid actuator  1  can be applied to various driving units including one for driving a valve for opening and closing an EGR pipe, one for driving fuel injection valves, and others for driving various kinds of driven members of the engine. 
     It is further understood by those skilled in the art that the foregoing is a preferred embodiment of the invention, and that various changes and modifications may be made without departing from the spirit and scope thereof.