Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Reexamination Certificate
2002-01-25
2004-10-19
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
C335S251000
Reexamination Certificate
active
06806802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic driving device, in which a movable core is supported in a housing portion which co-operates with the movable core to form an electromagnetic circuit, and a flow rate controlling apparatus employing the electromagnetic driving device.
2. Description of the Related Art
In an electromagnetic driving device in which an electromagnetic circuit is constituted by a movable core, a housing portion for housing therein the movable core in such a manner as to move in a reciprocating fashion and an attracting portion for attracting the movable core in one of reciprocating directions by virtue of magnetic attraction, it is known, as a means for supporting the movable core in such a manner as to move in the reciprocating fashion, to carry a shaft press fitted in the movable core on a bearing or to support the movable core with a plate spring. With these supporting means, since the housing portion and the movable core do not slide on each other and therefore the resistance value of, for example, friction generated by the reciprocating movement of the movable core is not affected by the value of electric current that is supplied to a coil of the electromagnetic driving device, the reciprocating positions of the movable core remain substantially constant both in increasing and decreasing directions of the value of electric current that is supplied to the coil in case the current value remains the same. Namely, the hysteresis of the reciprocating positions of the movable core is small relative to electric current that is supplied to the coil.
However, since the movable core is supported by the housing portion which houses therein the movable core in such a manner as to reciprocate and co-operates with the movable core for formation of an electromagnetic circuit and the bearing or plate spring which is a separate member, there may occur a case in which the axial centers of the housing and the movable core deviate from each other. If the axial centers of the housing and the movable core deviate from each other, the movable core slides on the housing portion locally, whereby there may be a risk of imbalanced wear of the movable core. In order to prevent the occurrence of imbalanced wear due to such an axial center deviation, it is a general practice to provide a larger gap between the movable core and the housing portion in a radial direction which is normal to the direction in which the movable core reciprocates so as to prevent the movable core from sliding on the housing portion locally. However, with the larger gap formed between the movable core and the housing in the radial direction, the magnetic flux which flows through the magnetic circuit constituted by the housing portion, the attracting portion and the movable core, lowers, and an attracting force acting between the movable core and the attracting portion lowers in turn. Then, if the number of turns of the coil is increased in order to prevent reduction in the magnitude of the attracting force, there is caused a problem that the size of the electromagnetic driving device is enlarged.
With a view to solving the problem, it is considered that the gap formed radially between the housing portion and the movable core should be made as small as possible by allowing the movable core to be supported directly on the housing portion. Even in the construction in which the housing portion directly supports the movable core, in order for the movable core to slide smoothly, a gap is formed in a radial direction between an inner circumferential wall of the housing portion and an outer circumferential wall of the movable core (hereinafter, the “gap formed in the radial direction between the inner circumferential wall of the housing portion and the outer circumferential wall of the movable core” is referred to as a side gap). However, if the movable core becomes eccentric relative to the housing portion when the movable core reciprocates, there is generated a portion where the side gap becomes narrow locally, and a force with which the movable core is attracted in the radial direction by the housing portion (hereinafter, the “force with which the movable core is attracted in the radial direction by the housing portion” is referred to as a “side force”) becomes large.
Furthermore, a sliding resistance generated between the housing portion and the movable core increases as the value of electric current supplied to the coil increases. Therefore, the hysteresis of the reciprocating positions of the movable core relative to the electric current value becomes large in increasing and decreasing directions of the value of electric current that is supplied to the coil. For example, in a case where an electromagnetic driving device is used in a flow rate controlling apparatus, there is caused a problem that the flow rate or the fluid pressure becomes different between the increasing direction and the decreasing direction of electric current.
SUMMARY OF THE INVENTION
An object of the present invention it to provide an electromagnetic apparatus in which a movable core is supported by a housing portion, in which the hysteresis of reciprocating positions of the movable core is small relative to the value of electric current that is supplied to a coil and which can be miniaturized, and a flow rate controlling apparatus employing the same driving device.
With any of an attracting portion, a housing portion and a movable core being set to become magnetically saturated with an electric current value which exceeds 60% of the maximum value of electric current that is supplied to a coil, a large side force acts between the housing portion and the movable core as the value of electric current that is supplied to the coil increases and approaches the electric current value at which the magnetic saturation occurs. In particular, when the movable core becomes eccentric relative to the housing portion so that a side gap becomes partially narrow or the movable core is brought into contact with the housing portion the side force increases drastically. Thus, when the side force increases there occurs a large resistance acting between the housing portion and the movable core. Consequently, the hysteresis of the reciprocating positions of the movable core increases relative to the electric current value in increasing and decreasing directions of electric current that is supplied to the coil.
When used herein, that a certain member is saturated magnetically means a state in which the magnetic flux density thereof increases to be so dense that no more magnetic flux is allowed to flow through the member. A state is not referred to as being magnetically saturated in which only part of the member such as a corner portion thereof becomes saturated but move magnetic flux can flow through the remaining portion of the member.
In addition, if any of the attracting portion, the housing portion and the movable core becomes saturated magnetically with an electric current value which is smaller than 40% of the maximum electric current value, the attracting force acting between the movable core and the attracting portion does not increase and therefore, in order to obtain a required travel, the number of turns of the coil must be increased.
Then, to cope with this, according to a first aspect of the present invention, there is provided an electromagnetic driving device in which any of an attracting portion, a housing portion and a movable core is set to become magnetically saturated when the value of electric current that is supplied to a coil increases to become a predetermined value which is between 40% or larger and 60% or smaller than the maximum value of electric current so supplied to the coil. Since magnetic saturation occurs when the electric current value reaches the predetermined value which is equal to or smaller than 60% of the maximum electric value, even if the movable core is eccentric relative to the housing portion, the upper limit value of the side force acting between the h
Ando Motoyoshi
Nakane Hiroyuki
Oishi Kenichi
Denso Corporation
Donovan Lincoln
Nixon & Vanderhye PC
LandOfFree
Electromagnetic driving device and flow rate controlling... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electromagnetic driving device and flow rate controlling..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electromagnetic driving device and flow rate controlling... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3266655