Electromagnetic actuator

Details Electromagnetic actuator Electromagnetic actuator

2000-04-18

2001-09-18

Barrera, Ramon M. (Department: 2832)

Electricity: magnetically operated switches, magnets, and electr

Magnets and electromagnets

With magneto-mechanical motive device

C335S255000, C335S262000

Reexamination Certificate

active

06292077

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an electromagnetic actuator for operating a movable iron core inserted through a central hole of an electromagnetic coil in the axial direction of the central hole by conducting a current through the electromagnetic coil, and more particularly relates to an electromagnetic actuator, having a large stroke, which is capable of producing a large thrust upon starting the electromagnetic actuator by conducting a current.
RELATED ART
Although well known is an electromagnetic actuator in that a movable iron core inserted through a central hole of an electromagnetic coil is made to be driven in the axial direction of the central hole by conducting a current through the electromagnetic coil, ordinarily, a thrust of the electromagnetic actuator is small upon starting thereof by conducting a current, and the thrust gradually increases after the electromagnetic actuator is started, as shown by a dotted line in FIG.
6
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However, for example, in operation (forcing out on a roller conveyor, pushing out from a shooter, or the like) of a variety of apparatuses and members of a manufacturing line, when a driving instruction signal of any sort is outputted, there are not a few occasions where an operation in response to the signal, for example, an operation of forcing out an object, or the like, is required to be performed as quickly as possible. In such an occasion when a quick operation is to be performed, a comparatively larger force is required for activation. For example, for forcing out an object of a certain weight, or activating a movable member, a force for activating it is required, while once it is activated, in many occasions, a large force is no more required as the operation can be continued by the inertia force. Therefore, if a thrust upon starting is increased and responsibility of an operation is improved, processing time in a variety of manufacturing lines can be shortened, and productivity thereof can be increased. Of course, when a driving instruction signal is outputted, the necessity for performing the quickest possible responsive operation is not limited to such problems of the manufacturing lines but also exists in a variety of technical fields.
For all that, a conventional electromagnetic actuator, having a small thrust upon starting by a conducted current as described heretofore, is unsuitable for such requirement, and in order that the requirement is satisfied by an actuator, the actuator is required to have a sufficiently increased thrust upon starting. However, the thrust upon starting cannot be so much increased as to cause a damage to an object on which the thrust is applied, and therefore it is also necessary to somewhat adjust the thrust while sufficiently increasing the thrust upon starting.
DISCLOSURE OF INVENTION
The present invention has been made to solve such problems, and a technical object thereof is to provide an electromagnetic actuator having a large stroke which is adapted to maximize a thrust thereof upon starting when a movable iron core is started to advance from the retreated stroke end.
Another technical object of the present invention is to provide an electromagnetic actuator, a thrust thereof is made to be somewhat adjustable while producing the maximum thrust upon starting of the electromagnetic actuator.
Still another technical object of the present invention is to provide the above-described actuators which are simple in structure and easy to manufacture.
In order to achieve the above-described technical objects, an electromagnetic actuator of the present invention has an electromagnetic coil, a magnetic frame made of a magnetic material arranged on the periphery of the electromagnetic coil, and a movable iron core which is inserted through a central hole of the coil and is slidable in the axial direction of the central hole of the coil, and the electromagnetic actuator is characterized by comprising a first sleeve which is made of a magnetic material to be magnetically coupled with the magnetic frame at one end side of the central hole of the coil, and mutually engaged with the movable iron core over the entire stroke of the movable iron core, and a second sleeve which is made of a magnetic material to be magnetically coupled with the magnetic frame at the other end side of the central hole, and spaced apart from the first sleeve, and an end thereof opposing the first sleeve is in close proximity to the movable iron core at the maximum stroke end but not in engagement therewith.
In the electromagnetic actuator having the above-described configuration, when a current is conducted through the electromagnetic coil in a state a movable iron core is at the retreated stroke end, a magnetic flux is generated on a periphery of the coil. However, since there is a space in the axial direction between the first sleeve and the second sleeve, the magnetic flux passes through inside the movable iron core for the space. At this time, since an end of the second sleeve opposing the first sleeve is extended to a position in close proximity to the movable iron core, when the magnetic flux passes the portion in high density, a large electromagnetic attraction in the axial direction is exerted between the second sleeve and the movable iron core, and accordingly, the maximum thrust can be produced in the movable iron core upon starting by conducting a current.
When the movable iron core is started to move and a portion thereof is inserted into the second sleeve, components in the radiating direction of the magnetic flux between the second sleeve and the movable iron core increase, and the electromagnetic attraction being exerted in the axial direction between them is gradually oriented toward the radiating direction which orthogonally crosses the thrust. Since the oriented force increases in proportion to an area of the second sleeve overlapped with the movable iron core, in accordance with moved amount of the movable iron core, the thrust gradually decreases.
However, as driving of an object to be driven can be started by the maximum thrust available upon starting of the electromagnetic actuator described above, the desired objects can be attained.
In the above-described electromagnetic actuator, the diameter of the front end at the second sleeve side of the movable iron core can be reduced for adjusting the thrust upon starting, thereby the thrust can be somewhat adjusted while producing the maximum thrust in the vicinity of the retreated stroke end.
Further, the first sleeve and the second sleeve can be concentrically joined by a bobbin which is wound by an electromagnetic coil, or a guide tube made of a nonmagnetic material can be inserted into the first sleeve and the second sleeve to have them concentrically joined, thereby the movable iron core can be operated in a stabilized way.
Furthermore, in the above-described electromagnetic actuator, the first sleeve and/or the second sleeve can be formed by rolling a plate made of a magnetic material, thereby enabling to provide the electromagnetic actuator which is simple in structure and easy to manufacture.


REFERENCES:
patent: 4422060 (1983-12-01), Matsumoto et al.
patent: 4558293 (1985-12-01), Haneda et al.

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