ELECTROMAGNETIC ACTUATOR

A solenoid valve includes first and second attraction portions in the interior of a housing disposed on an upper part of a valve body. A movable iron core, which confronts the first and second attraction portions, is disposed displaceably in the housing. Further, in the interior of the first attraction portion, which is recessed in a concave shape, a first guide body is installed, the first guide body being formed in a cylindrical shape from a non-magnetic material, and a first rod member of the movable iron core is supported displaceably in axial directions by the first guide body. On the other hand, a cylindrically shaped second guide body is disposed on a lower end of the housing, and a second rod member of the movable iron core is supported displaceably in the axial directions by the second guide body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A solenoid valve10is provided, for example, in a fuel cell system, which is capable of adjusting the flow rate of a fuel (hydrogen) supplied from a non-illustrated pressure control unit. As shown inFIGS. 1 and 2, the solenoid valve10includes a valve body12having a passage therein through which the fuel flows, a solenoid unit14connected to an end of the valve body12, and a valve mechanism18including a valve element16that is moved in axial directions (the directions of arrows A and B) under an excitation action of the solenoid unit14. The solenoid unit14functions as en electromagnetic actuator for actuating the valve element16.

The valve body12is formed, for example, in a bottomed cylindrical shape from a metal material, is formed with a supply port20through which the fuel is supplied and which projects in a lateral direction, and further is formed with a discharge port26that projects downwardly from a central portion thereof. Further, a communication chamber32is formed in the interior of the valve body12, the communication chamber32opening upwardly and communicating with the supply port20and the discharge port26. In addition, the valve mechanism18, to be described later, is disposed in the interior of the communication chamber32. A bottom surface of the communication chamber32serves as a valve seat38on which the valve element16of the valve mechanism18is seated.

The solenoid unit14includes a bottomed cylindrical shaped housing40disposed on an upper part of the valve body12, and a movable iron core46, which is disposed displaceably in the axial direction of the housing40.

The housing40is formed, for example, from a metal material having a dividable U-shape in cross section, and is arranged in a condition of opening toward a side of the valve body12(in the direction of the arrow B). A fixed iron core member (fixed iron core)50is formed substantially in the center of the housing40. A coil42is wound and accommodated on an outer circumferential side of the fixed iron core50, and a connector unit52, which is connected electrically to the coil42, is disposed on a side of the housing40. In addition, in a state in which a non-illustrated connector is connected to the connector unit52, electric power from a power source is supplied to the coil42via the connector unit52.

Further, in the interior of the housing40, a first attraction portion56is formed, which is recessed upwardly (in the direction of the arrow A) in the center of the fixed iron core50, and a second attraction portion58is formed more toward the side of the valve body12(in the direction of the arrow B) than the first attraction portion56. The first and second attraction portions56,58are offset mutually in the axial direction (the direction of arrows A and B) of the housing40, with the first attraction portion56being arranged on the center side of the housing40, and the second attraction portion58being arranged on an outer circumferential side with respect to the first attraction portion56.

The first attraction portion56opens downwardly (in the direction of the arrow B) and has first and second stepped portions60,62, which project with respect to a bottom portion thereof toward the side of the valve body12, and the first and second stepped portions60,62are diametrically expanded toward the outer circumferential side. The first stepped portion60is formed on the inner circumferential side, and the second stepped portion62is formed on the outer circumferential side with respect to the first stepped portion60. Together therewith, the first stepped portion60projects in an annular shape toward the side of the valve body12(in the direction of the arrow B) at a predetermined height with respect to the bottom portion, and the second stepped portion62projects toward the side of the valve body12further (in the direction of the arrow B) with respect to the first stepped portion60.

In addition, a cylindrical first guide body (bearing)64is installed on an inner circumferential surface of the first attraction portion56in facing relation to the second stepped portion62. The first guide body64, for example, is formed from a non-magnetic material, and is installed by press-insertion thereof coaxially with the first attraction portion56. More specifically, the first guide body64is made from a resin material such as Teflon (registered trademark) having a small coefficient of friction.

The second attraction portion58is constituted from a third stepped portion66, and a fourth stepped portion68formed on an outer circumferential side of the third stepped portion66. The fourth stepped portion68is formed in a stepped shape on the side of the valve body12(in the direction of the arrow B) with respect to the third stepped portion66.

The movable iron core46includes a main body portion70, which is formed in a cylindrical columnar shape, for example, from a magnetic material, a first rod member72formed on an upper part of the main body portion70and which is movable inside the first attraction portion56, and a second rod member74formed on a lower part of the main body portion70and connected to the valve element16.

The first and second rod members72,74are formed coaxially with the main body portion70and are reduced in diameter with respect to the main body portion70, as shafts having substantially the same diameter, respectively. Further, an end of the first rod member72is formed with a stepped shape corresponding to the first stepped portion60of the first attraction portion56, and an end of the main body portion70on the side of the first rod member72is formed with a stepped shape corresponding to the third and fourth stepped portions66,68of the second attraction portion58.

Additionally, the first rod member72, which is inserted in the first attraction portion56, is guided highly precisely in the axial directions (the directions of arrows A and B) by being in sliding contact with the inner circumferential surface of the first guide body64.

On the other hand, the lower end of the housing40projects downwardly in a cylindrical shape (in the direction of the arrow B), is inserted into the communication chamber32of the valve body12, and is formed with an accommodation hole76therein that penetrates in the axial direction.

A cylindrical second guide body (bearing)80is installed in the accommodation hole76in abutment against (contact with) an inner circumferential surface of the accommodation hole76, and the second rod member74is guided highly precisely in the axial directions (the directions of arrows A and B) by being in sliding contact with the inner circumferential surface of the second guide body80. The second guide body80, for example, is formed from a non-magnetic material, and is installed by press-insertion thereof coaxially with the accommodation hole76. More specifically, the second guide body80is made from a resin material such as Teflon (registered trademark) having a small coefficient of friction, as with the first guide body64.

Further, the second guide body80is formed with substantially the same diameter as the first guide body64. More specifically, the dimensional tolerance of the inner circumferential surface with which the second rod member74is in sliding contact is set equivalently with the dimensional tolerance of the inner circumferential surface of the first guide body64with which the first rod member72is in sliding contact.

The valve mechanism18includes the valve element16, which is connected to a lower part of the movable iron core46, and a spring84, which is interposed between the valve element16and the housing40.

The valve element16is formed substantially in the shape of a disk, and includes a shaft88, which is screw-engaged in a screw hole86formed in the second rod member74of the movable iron core46, and a valve member90formed on a lower end of the shaft88. Additionally, an annular seat member92is mounted on an end face of the valve member90in confronting relation to the valve seat38. The valve member90is expanded in diameter in a radial outward direction with respect to the shaft88. The seat member92is made up, for example, from an elastic material such as rubber or the like, and a part of the seat member92that is seated on the valve seat38projects in a direction away from the valve member90.

The spring84, for example, is constituted from a coil spring, which is coiled or wound in a helical shape, and is interposed between the valve member90of the valve element16and the end surface of the housing40. The valve element16is urged in a downward direction (the direction of the arrow B) by an elastic force of the spring84.

The solenoid valve10, to which an electromagnetic actuator according to the embodiment of the present invention is applied, is constructed basically as described above. Next, operations and advantages of the solenoid valve10will be described below.FIG. 1shows a non-excited condition in which electric energy is not applied to the coil42, i.e., a valve-closed state in which the movable iron core46is displaced toward the side of the valve seat38(in the direction of the arrow B) by the elastic force of the spring84, and then the seat member92of the valve element16is seated on the valve seat38, whereby communication between the supply port20and the discharge port26is blocked.

In such a valve-closed state, a non-illustrated power supply is activated to energize the coil42, whereby the coil42is excited, and under the excitation of the coil42, the movable iron core46is attracted toward the first and second attraction portions56,58. At this time, the magnetic circuit is formed as a closed magnetic circuit in which magnetism generated by the coil42flows from the first attraction portion56through the first rod member72of the movable iron core46, and from the second attraction portion58through the main body portion70of the movable iron core46, and is returned again to the housing40.

In addition, as shown inFIG. 2, the movable iron core46is displaced upwardly (in the direction of the arrow A) under a condition in which the first rod member72is supported by the first guide body64, and the second rod member74is supported by the second guide body80, and accordingly, the valve element16, which is connected to the movable iron core46, is raised upwardly away from the valve seat38to result in a valve-open state. Consequently, the supply port20and the discharge port26of the valve body12are placed in communication with each other through the communication chamber32, whereby fuel supplied to the supply port20passes through the communication chamber32and flows to the discharge port26. Thus, the fuel is supplied to an external apparatus, which is connected on a downstream side from the discharge port26.

On the other hand, by stopping supply of electricity to the coil42and placing the solenoid unit14including the coil42in the non-excited condition, the attractive force with respect to the movable iron core46is extinguished, whereupon the movable iron core46is pressed toward the side of the valve seat38(in the direction of the arrow B) by the elastic force of the spring84. In addition, by lowering the valve element16together with the movable iron core46, the seat member92of the valve element16is seated on the valve seat38, and the valve-closed state is brought about in which communication between the supply port20and the discharge port26is blocked (seeFIG. 1).

In this case as well, since the movable iron core46is displaced under a condition in which the first rod member72is supported by the first guide body64, and the second rod member74is supported by the second guide body80, the movable iron core46can be moved highly precisely in the axial direction (in the direction of the arrow B).

As described above, according to the present embodiment, the first and second guide bodies64,80, which are formed in cylindrical shapes from a non-magnetic material, are disposed respectively in the first attraction portion56and the accommodation hole76of the housing40, and the first rod member72and the second rod member74of the movable iron core46are inserted in the interiors of the first and second guide bodies64,80thereby to be guided in the axial directions (the directions of arrows A and B). Owing thereto, it is unnecessary to carry out a highly precise process in order to guide the movable iron core46with respect to the housing40, and by manufacturing the separately-formed first and second guide bodies64,80beforehand with high precision, with a simple structure having the first and second guide bodies64,80installed therein, the movable iron core46can be guided axially with high precision in the axial directions (the directions of arrows A and B) and manufacturing costs can be suppressed.

Stated otherwise, without being tilted with respect to the axis of the housing40, the movable iron core46can be moved while being supported by the first and second guide bodies64,80.

Further, by integral formation of the first rod member72, which is supported by the first guide body64, on the main body portion70of the movable iron core46, compared to the conventional technique in which the movable iron core46and the rod portion supported by the guide body are constructed as separate members, the number of constituent parts can be reduced, together with reducing the number of assembly steps. Furthermore, by integral formation in this manner, since flow of magnetic flux between the movable iron core46and the first rod member72is enhanced, magnetic efficiency can be improved.

Further, in a similar manner, by integral formation of the second rod member74, which is supported by the second guide body80, on the main body portion70of the movable iron core46, compared to the conventional technique in which the movable iron core46and the rod portion supported by the guide body are constructed as separate members, the number of constituent parts can be reduced, together with reducing the number of assembly steps. Furthermore, by integral formation in this manner, since flow of magnetic flux between the movable iron core46and the second rod member74is enhanced, magnetic efficiency can be improved.

Furthermore, as a result of the first guide body64and the second guide body80being formed with the same diameter, since the guide bodies can be manufactured precisely with the same dimensional tolerance, compared to a situation in which the guide bodies are fabricated with different dimensions, the movable iron core46can be guided with higher precision in the axial directions (the directions of arrows A and B).

Still further, with the first and second guide bodies64,80, since the first and second guide bodies64,80can avoid being influenced by magnetism produced in the solenoid unit14, the magnetic force can be concentrated in the axial direction (the direction of arrows A and B), and thus the attractive force applied to the movable iron core46in the axial direction can be enhanced.

The electromagnetic actuator according to the present invention is not limited to the above embodiment. Various changes and modifications may be made to the embodiment without departing from the scope of the invention as set forth in the appended claims.