Solenoid Apparatus

The present invention is directed to a solenoid apparatus and more particularly to a solenoid apparatus using a magnetic material yoke as the electrical ground.

A conventional solenoid apparatus is usually provided with a metal casing in which are incorporated a bobbin having a coil, a magnetic material core, a magnetic material plunger and a magnetic material yoke. In such a conventional solenoid apparatus, one end of the coil is usually connected to the casing so that the casing can be used as the ground line thereby reducing the number of wiring connections and assembling time. Generally, one end of the coil is connected to the casing by soldering or clinching, using an insulated lead wire.

In Japanese Utility Model Published Application No. 5956713, which is assigned to the same Assignee as the present application, it was proposed to form a resilient projection on the ground terminal of the coil which extends into resilient contact with the casing to electrically connect the projection to the casing by a subsequent clinching operation.

In recent years, the metal casing of conventional solenoid assemblies has been replaced by a casing made of synthetic resin material because of the lower cost. In such a case, it is not possible to use the casing as the ground line and therefore, a separate lead wire must be provided for the ground which must be connected to the common ground line such as a grounded body upon assembling of the solenoid. As a result, there are drawbacks since the number of wires and the assembling time are increased.

It is an object of the present invention to provide a solenoid apparatus which is capable of using a synthetic resin casing and to reduce the number of parts and assembling time.

It is a further object of the present invention to provide a solenoid apparatus having a core of magnetic material, a plunger of magnetic material movably disposed at one end of said core, a bobbin surrounding at least a portion of said core and plunger, an electric coil wound on said bobbin, a first terminal mounted on said bobbin and connected to one end of said electric coil and having a first connection arm electrically connected thereto, a second terminal mounted on said bobbin and connected to the other end of said electric coil, a yoke of magnetic material connected to the opposite end of said core and covering at least a portion of said electric coil and a second connection arm connected to said yoke and said first connection arm to electrically connect said bobbin coil to said yoke.

The foregoing and other objects, features and advantages of the present invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings.

FIG. 1 is a partially cutaway perspective view of a solenoid valve according to a preferred embodiment of the present invention;

FIG. 2 a transverse sectional view of the solenoid valve of FIG. 1;

FIG. 3 is a fragmentary perspective view of the solenoid valve of FIG. 1;

FIG. 4 is a fragmentary perspective exploded view of the solenoid valve of FIG. 1; and

FIG. 5 is a fragmentary perspective view of a solenoid valve according to another modification.

In the embodiment of the invention as disclosed in FIGS. 1-4, the solenoid valve is disposed in a casing made of molded synthetic resin material. The yoke 1 has a U-shaped configuration and is made of magnetic material. A part corresponding to the base of the U-shaped yoke 1 is connected to the rear end of a core 2. Each end of the yoke is connected to a metallic base plate 11 and the casing. A sleeve 2b of magnetic material covers the outer circumference of the core 2 and extends to the left of the core as viewed in FIG. 2 for slidably guiding the plunger 9. A bobbin 3 is mounted on the outer surface of the sleeve 2 b and an electric coil 6 is wound thereon. A valve member 9a is secured to the end of the plunger 9 opposite the core 2. A coil spring 10 is compressed between the plunger and the core 2 for biasing the plunger 9 to the left as viewed in FIG. 2 into engagement with a valve seat 11a which surrounds the output port 11b in the base plate 11. An input port 11c is also provided in the base plate 11. As shown in FIG. 2, the plunger 9 is biased by the spring 10 into engagement with the valve seat 11a to close the output port 11b.

When the electric coil 6 is energized, a magnetic flux is generated along the axis of the coil so as to draw the plunger 9 toward the core 2 against the bias of the spring 10. Thus, the valve member 9a will move away from the valve seat 11a thereby providing communication between the input port 11c and the output port 11b.

As shown in FIG. 4, the side edge of the U-shaped yoke 1 is formed with with an L-shaped projection 1b which is of integral one piece construction with the yoke so as to be electrically connected thereto. The L-shaped projection is provided with a pointed connection arm 1c. A circular hole 1a is provided in the center of the base of the U-shaped yoke 1 and a cylindrical projection 2a is formed on one end of the core 2. The projection 2a is fitted in the hole la and secured therein by any suitable means such as swaging or peening.

The bobbin 3 is provided with flange portions 3a and 3b on opposite ends of a hollow tube 3c. A socket member 3d is secured on the flange 3a and is provided with a socket 3e for receiving the ground terminal 4 and a socket 3f for receiving the positive terminal 5, as shown in FIGS. 1, 3 and 4. The ground terminal 4 is comprised of a copper plate having a receiving arm 4a with a U-shaped groove 4b therein, a plug portion 4c and a wire connection part 4d. The receiver arm 4a is bent upwardly out of the plane of the copper plate and the wire connection part 4d is bent downwardly and rearwardly relative to the plane of the copper plate. The positive terminal 5 has substantially the same configuration as the ground terminal and is provided with a wire receiving portion 5a, a plug portion 5c and a wire connection portion 5d. The plug portion 4c of the ground terminal 4 is inserted and electrically connected to the socket 3e and the plug portion 5c is inserted in and electrically connected to the socket 3f.

The electric coil 6 is formed by winding a wire covered with insulating paint on the tubular portion 3c of the bobbin 3. At the beginning of the winding operation, one end of the wire is fixed temporarily to the wire connection part 5d of the positive terminal 5. At the completion of the winding, the opposite end of the wire forming the electric coil is fixed temporarily to the wire connection portion 4d of the ground terminal 4. Subsequently, the wire ends are permanently secured to the wire connection portions 4d and 5d by a clinching operation. The insulating paint on each end of the wire is melted by heating, whereby an electrically conductive coupling is provided between the wire and the terminals. The heating of the wire is achieved by passing electricity through the wire.

The bobbin 3 having the electric coil 6 wound thereon is connected to the yoke 1 and the core 2 which were previously connected together as shown in FIG. 3. The connection arm 1c formed on the yoke 1 is inserted in the U-shaped groove 4b formed in the receiver arm 4a of the ground terminal 4 upon sliding the bobbin over the core. The connection arm 1c is then electrically connected to the receiver arm 4a by soldering. The other elements of the solenoid valve are then assembled and one end of the lead wire 7 as shown in FIG. 3 is disposed in the U-shaped groove 5b of the receiver arms 5a of the positive terminal 5 and electrically connected thereto by means of soldering. The casing 8 is formed by resin mold to complete the solenoid valve assembly as shown in FIG. 1.

In the solenoid valve assembly according to the present invention, the ground connection is provided through the ground terminal 4, connection arm 1c, the yoke 1 and the base plate 11. In the embodiment of FIGS. 1-4 inclusive, the connection arm 1c is formed of integral, one piece construction with the yoke 1. However, the embodiment as shown in FIG. 5 the yoke and the connection arm are separately formed and the connection arm 1d which is comprised of a copper plate, is secured to a corresponding portion of the base of the U-shaped yoke 1 by spot welding.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those in the art that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.