FIG. 13 shows an example of a conventional solenoid of this type. FIG. 13 is a schematic sectional view of a conventional solenoid.
A solenoid 101 is formed by combining a molded coil 102 and a solenoid main body 103 with each other into an integral unit.
The molded coil 102 includes a coil 104 wound around thereon, and, at the center of the coil 104, there is formed a hole 105 recessed facing the solenoid main body 103.
Further, in the portion of the molded coil 102 on the side opposite to the solenoid main body 103, there is provided an annular plate 106 which is adjacent to the coil 104, and, from the plate 106 onward, there is provided a mold portion 107 forming the bottom surface of the hole 105. In the mold portion 107, a coil wire 108 led out of the coil 104 is connected to a lead wire 109.
The solenoid main body 103 is equipped with a column portion 110 which constitutes a core portion thereof and which is to be inserted into the hole 105 of the molded coil 102, and a case 111 spaced apart from the column portion 110 through the intermediation of the annular space in which the molded coil 102 is arranged and covering the outer periphery of the molded coil 102.
The column portion 110 of the solenoid main body 103 is equipped with center post 112 formed integrally with the case 111, a plunger 113 magnetically attracted to the center post 112 through energization of the coil 104, a rod 114 connected to the plunger 113, a bearing 115 supporting the rod 114, a cap 116 covering the forward end portion of the column portion 110, and a guide 117 smoothening the outer periphery between the cap 116 and the center post 112 to facilitate the insertion of the column portion 110 into the hole 105 of the molded coil 102.
A shim 118 is arranged on the inner side of the center post 112.
The center post 112 extends from the inner end of an annular radial portion 119 toward the molded coil 102. Further, the case 111 also extends from the outer end of the annular radial portion 119 toward the molded coil 102.
And, caulking fixation is effected on the end portion of the case 111 and the corner portion of the molded coil 102, whereby the molded coil 102 and the solenoid main body 103 are integrated with each other.
In the solenoid 101, constructed as described above, by supplying electric current to the coil 104 through the lead wire 109, a magnetic circuit is formed, where a current passes through: the center post 112, the case 111, the plate 106, and the plunger 113, and back to 112. The plunger 113 is magnetically attracted to the center post 112.
When no electric current is being supplied to the coil 104, the plunger 113 is spaced apart from the center post 112 as shown in the drawing under the urging force of a spring or the like (not shown).
However, in this conventional solenoid 101, in which the molded coil 102 and the solenoid main body 103 are integrated with each other by caulking fixation, the presence of the lead wire 109 constitutes an obstacle when the solenoid 101 is mounted to an associated hydraulic/pneumatic control apparatus, resulting in a rather poor mounting operability.
Further, in the assembly line for assembling the hydraulic/pneumatic control apparatus concerned, the presence of the lead wire 109 constitutes an obstacle even in the process after the mounting of the solenoid 101 to the hydraulic/pneumatic control process, resulting in a rather poor operability.
Further, when the solenoid 101, composed of the molded coil 102 and the solenoid main body 103 integrated with each other through caulking fixation, is mounted to the associated hydraulic/pneumatic control apparatus by welding, heat load is applied to the molded coil 102, which entails the need for special consideration during operation. Otherwise, welding cannot be selected as the mounting method.
And, in an apparatus involving coating as in the case of a shock absorber, coating is first performed separately on the apparatus and the case 111 of the solenoid main body 103, and then the molded coil 102 and the solenoid main body 103 are integrated into one through caulking fixation. Thereafter, the solenoid 101, formed into an integral unit, is mounted to the apparatus, which means coating has to be performed separately on the apparatus and the case 111, resulting in a rather poor operability.