1. Technical Field
The present invention relates to a compact electrostatic relay (electrostatic micro-relay), specifically to a structure of a secondary spring that elastically restores a movable portion in an electrostatic relay.
2. Related Art
In the electrostatic relay, when a moving contact is brought into contact with a fixed contact, an electrostatic actuator is driven to displace the moving contact. When the moving contact and the fixed contact are separated from each other, the moving contact is separated from the fixed contact by an elastic restoring force of a movable spring that is elastically deformed in driving the electrostatic actuator.
In driving the electrostatic actuator, a DC voltage is applied between a movable electrode and a fixed electrode, and the movable electrode is attracted to the fixed electrode by an electrostatic force that acts between the electrodes, thereby displacing a member in which the movable electrode is provided. However, in the electrostatic actuator, due to electrostatic induction or induction polarization generated between the electrodes, occasionally the movable electrode is attracted to and not separated from fixed electrode even if the DC voltage applied between the movable electrode and the fixed electrode is turned off. Further, occasionally the moving contact and the fixed contact are not separated by an adhesive force that is generated when the fixed contact and the moving contact come into contact with each other. Therefore, when the movable electrode is attracted to the fixed electrode, or when the moving contact is in contact with the fixed contact, it is necessary to increase a spring modulus of the movable spring.
For example, Japanese Unexamined Patent Publication No. 6-203726 discloses a contact switchgear in which the spring modulus of the movable spring is increased when the moving contact comes into contact with the fixed contact.
When a rear surface of the movable spring 13 is pressed by a driving member 18, the movable spring 13 is elastically curved, and the leading end portion of the movable spring 13 abuts on the leading end 17a of the operation controlling member 17. When the movable spring 13 is further pressed by the driving member 18, the moving contact 14 is pressed on the fixed contact 16 to close between the moving contact 14 and the fixed contact 16. In the contact switchgear disclosed in Japanese Unexamined Patent Publication No. 6-203726, the movable spring 13 abuts on the operation controlling member 17 before the moving contact and the fixed contact come into contact with each other, thereby achieving shock relaxation of the contact and reduced contact bounce time.
In the contact switchgear disclosed in Japanese Unexamined Patent Publication No. 6-203726, when the moving contact 14 is brought into contact with the fixed contact 16, the movable spring 13 abuts on the leading end 17a of the operation controlling member 17 to increase the spring modulus of the movable spring 13. However, in the contact switchgear disclosed in Japanese Unexamined Patent Publication No. 6-203726, because a driving force of the driving member 18 is the electromagnetic force, the spring modulus of the movable spring 13 is not increased in order to separate the movable electrode and fixed electrode of the electrostatic actuator. Additionally, in the contact switchgear, while the moving contact 14 is in contact with the fixed contact 16, the movable spring 13 is separated from the leading end 17a of the operation controlling member 17 as shown in
Japanese Unexamined Patent Publication No. 2000-164104 discloses an electrostatic micro-relay, in which a movable substrate having a spring property is overlapped on a substrate in which a fixed contact and a fixed electrode are provided, and a moving contact that is opposite the fixed contact and a movable electrode that is opposite the fixed electrode are provided in a lower surface of the movable substrate. In the electrostatic micro-relay, a projection portion is provided in at least one of the movable electrode and the fixed electrode, the projection portion is brought into contact with the other of the movable electrode and the fixed electrode before the moving contact and the fixed contact abut on each other, and the opening force is increased by an elastic deformation partially generated in the movable spring near the projection portion.
In the electrostatic relay, although the original spring modulus of the movable spring can arbitrarily be increased by a position or a height of the projection portion, there is a restriction to the position or the height, and a degree of freedom of design is degraded by processing preciseness or troublesome design.
One or more embodiments of the present invention increases an opening force when the movable electrode is separated from the fixed electrode, to simplify the structure, and to enhance the degree of freedom of the design in an electrostatic relay in which the moving contact and the movable electrode are displaced in parallel with the base substrate.
In accordance with one or more embodiments of the present invention, an electrostatic relay includes: a base substrate; a fixed contact portion that is fixed to the base substrate, the fixed contact portion including a fixed contact; a moving contact portion that includes a moving contact to be brought into contact with or separated from the fixed contact; a fixed electrode portion that is fixed to the base substrate; a movable electrode portion that is displaced along with the moving contact portion toward a direction parallel to the base substrate by an electrostatic force generated between the fixed electrode portion and the movable electrode portion; a first spring member that returns the displaced movable electrode portion to an original position; and a second spring member that abuts on one of a fixed portion fixed to the base substrate and the movable electrode portion or a movable portion displaced along with the movable electrode portion while being not deformed until abutting on one of the fixed portion and the movable electrode portion or the movable portion before the moving contact portion abuts on the fixed contact when the moving contact portion and the movable electrode portion are displaced, the second spring member being provided in the other of the fixed portion and the movable portion. The fixed portion is a member that is fixed to the base substrate. The fixed portion may be the fixed contact portion or the fixed electrode portion or a fixed member (for example, the spring supporting portion) except the fixed contact portion and the fixed electrode portion. The movable member may be the moving contact portion or a member except the moving contact portion. However, when the member in which the second spring member is provided is the fixed electrode portion or the fixed contact portion while the member on which the second spring member abuts is the movable electrode portion or the moving contact portion, or when the member in which the second spring member is provided is the movable electrode portion or the moving contact portion while the member on which the second spring member abuts is the fixed electrode portion or the fixed contact portion, it is necessary that the second spring member has an insulating property.
In the electrostatic relay according to one or more embodiments of the present invention, the second spring member that is different from the first spring member is provided in the other of the fixed portion and the movable electrode portion or the movable portion, and the second spring member is not deformed until abutting on one of the fixed member and movable electrode portion or the movable member. Therefore, the structure that elastically returns the movable electrode portion or the movable portion can be simplified to facilitate production of the electrostatic relay. Additionally, because the spring modulus of the second spring member and a moving distance of the movable portion in changing the spring modulus can independently be determined, the degree of freedom of the design is enhanced to facilitate the design of the electrostatic relay.
In the electrostatic relay according to one or more embodiments of the present invention, the second spring member is a plate spring that is fixed in a cantilever manner to the other of the fixed portion and the movable electrode portion or the movable portion. Accordingly, because the second spring member is formed into the cantilever shape, a displacement amount can be increased compared with the case where the second spring member is provided in a fixed-fixed beam manner, and the cantilever second spring member can deal with the large displacement amount of the movable portion.
In the electrostatic relay according to one or more embodiments of the present invention, the second spring member is not connected to one of the fixed portion and the movable electrode portion or the movable portion. Accordingly, the second spring member is not deformed until the second spring member abuts on one of the fixed member and the movable electrode portion or the movable member.
In the electrostatic relay according to one or more embodiments of the present invention, the second spring member abuts on a projection portion that is provided in one of the fixed portion and the movable electrode portion or the movable portion. Accordingly, a point of action of a force applied to the second spring member is changed by changing the position of the projection portion, so that the spring modulus of the second spring member can be changed.
In the electrostatic relay according to one or more embodiments of the present invention, a plate-shaped second spring member that is provided in a cantilever manner to the other of the fixed portion and the movable electrode portion or the movable portion can abut one a projection portion that is provided in one of the fixed portion and the movable electrode portion or the movable portion, and a length direction of the second spring member that is not deformed is parallel to a surface in which the projection portion is provided. Accordingly, the design is facilitated, because a distance between the projection portion and the second spring member is not changed even if the position of the projection portion is changed along a surface in which the projection portion is provided.
In the electrostatic relay according to one or more embodiments of the present invention, the second spring member is provided in a spring supporting portion fixed to the base substrate between the movable electrode portion and the fixed contact portion. Accordingly, the spring supporting portion that retains the second spring member can be provided by utilizing spaces on both sides of the moving contact portion.
In the electrostatic relay according to one or more embodiments of the present invention, second spring members are provided at positions that are symmetrical in relation to a center line of the movable electrode portion. Accordingly, because the second spring members are symmetrically provided, a force applied to the movable portion becomes asymmetric after the fixed portion or the movable portion abuts on the second spring member, and there is no risk of inclining the movable portion.
In the electrostatic relay according to one or more embodiments of the present invention, the first spring members are provided in both end faces in the direction in which the movable electrode portion is displaced, or the first spring members are provided opposite the end faces, respectively. Accordingly, because the movable electrode portion can float from the base substrate by retaining the movable electrode portion from both sides with the first spring member, the movable electrode portion can be stabilized.
In the electrostatic relay according to one or more embodiments of the present invention, the first spring member is provided in one of end faces in the direction in which the movable electrode portion is displaced, or the first spring member is provided opposite one of the end faces. Accordingly, because the first spring member is provided only on one side of the movable electrode portion, the structure of the electrostatic relay can be simplified and miniaturized.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. Furthermore, the present invention is not limited to the following embodiments, but various design changes can be made without departing from the scope of the present invention.
A fixed contact portion 33, a moving contact portion 34, a fixed electrode portion 35, a movable electrode portion 36, movable springs 37a and 37b (first spring member), and spring supporting portions 38 and 39 are provided in an upper surface of a base substrate 32 formed by an Si substrate in the electrostatic relay 31. In the electrostatic relay 31, a switch is formed by the fixed contact portion 33 and the moving contact portion 34, and an electrostatic actuator for opening and closing the switch is formed by the fixed electrode portion 35, the movable electrode portion 36, the movable springs 37a and 37b, and the spring supporting portions 38 and 39.
As shown in
The moving contact portion 34 is provided opposite the fixed contacts 46a and 46b. In the moving contact portion 34, an SiN insulating layer 53 is formed on an upper surface of an Si moving contact substrate 51, and a contact layer 54 is formed on the insulating layer 53. An end face of the contact layer 54 that is opposite fixed contacts 46a and 46b is projected from a front face of the moving contact substrate 51 to constitute a moving contact 56.
The moving contact substrate 51 is supported in a cantilever manner by a support beam 57 that is projected from the movable electrode portion 36. The lower surfaces of the moving contact substrate 51 and support beam 57 float from the upper surface of the base substrate 32, and the moving contact substrate 51 and the support beam 57 can move along with the movable electrode portion 36 in a length direction (Y-direction) of the base substrate 32.
In the electrostatic relay 31, a main circuit (not shown) is connected to the metallic pad portions 45a and 45b of the fixed contact portion 33, and the main circuit can be closed by bringing the moving contact 56 into contact with the fixed contacts 46a and 46b. The main circuit can be opened by separating the moving contact 56 from the fixed contacts 46a and 46b.
An electrostatic actuator that moves the moving contact portion 34 includes the fixed electrode portion 35, the movable electrode portion 36, the movable springs 37a and 37b, and the spring supporting portions 38 and 39.
As shown in
As shown in
As shown in
The movable electrode portion 36 is formed by an Si movable electrode substrate 71, and the lower surface of the movable electrode substrate 71 floats from the upper surface of the base substrate 32. The support beam 57 is projected in the center of the end face on the moving contact side of the movable electrode portion 36, and the moving contact substrate 51 is retained at a leading end of the support beam 57.
The movable electrode portion 36 is retained by the movable spring 37a supported by the spring supporting portion 38 and the movable spring 37b supported by the spring supporting portion 39. As shown in
The spring supporting portion 39 made of Si extends in the X-direction in the rear end portion of the base substrate 32. The lower surface of the spring supporting portion 39 is fixed to the upper surface of the base substrate 32 by an insulating film 82. Coupling portions 83 are projected forward from both ends of the spring supporting portion 39, and the coupling portions 83 and the rear end face of the movable electrode portion 36 are connected by the pair of symmetrically-formed movable springs 37b made of Si. The movable spring 37b is formed into the plate shape or beam shape and disposed in parallel with the X-direction.
Accordingly, the movable electrode portion 36 is retained by the spring supporting portions 38 and 39 with the movable springs 37a and 37b interposed therebetween, and the movable electrode portion 36 is horizontally retained while floating from the upper surface of the base substrate 32. The movable electrode portion 36 can be displaced in the Y-direction by elastically deforming the movable springs 37a and 37b, and the movable electrode portion 36 is returned to an original position by elastic restoring forces of the movable springs 37a and 37b when the electrostatic force displacing the movable electrode portion 36 is released. Because each of the pair of movable springs 37a and the pair of movable springs 37b has the symmetrical shape, the movable electrode portion 36 can be displaced in the Y-direction while not being able to be displaced in the X-direction when the movable springs 37a and 37b are deformed to displace the movable electrode portion 36.
In the electrostatic relay 31 having the above-described structure, a DC voltage source is connected between the fixed electrode portion 35 and the movable electrode portion 36, and the DC voltage is applied by a control circuit. In the fixed electrode portion 35, one of terminals of the DC voltage source is connected to the electrode pad layer 64. The other terminal of the DC voltage source is connected to the spring supporting portion 39. The spring supporting portion 39 and the movable spring 37b have conductivity, and the spring supporting portion 39, the movable spring 37b, and the movable electrode portion 36 are electrically connected. Therefore, the voltage applied to the spring supporting portion 39 is applied to the movable electrode portion 36.
When the DC voltage is applied between the fixed electrode portion 35 and the movable electrode portion 36 by the DC voltage source, an electrostatic attractive force is generated between the branch portion 68 of the branch-shaped electrode 67 and the comb-shaped portion 73 of the comb-shaped electrode 72. However, because the structures of the fixed electrode portion 35 and movable electrode portion 36 are symmetrically formed in relation to a center line of each fixed electrode portion 35, the electrostatic attractive forces acting on the movable electrode portion 36 in the X-direction are balanced, and the movable electrode portion 36 does not move in the X-direction. On the other hand, because the distance from the branch portion 68 that is adjacent to each comb-shaped portion 73 and located closer to the moving contact portion 34 is shorter than the distance from the branch portion 68 that is adjacent to the comb-shaped portion 73 and located farther away from the moving contact portion 34, each comb-shaped portion 73 is attracted to the moving contact portion side, and the movable electrode portion 36 moves in the Y-direction while the movable springs 37a and 37b are bent. As a result, the moving contact portion 34 moves onto the side of the fixed contact portion 33, and the moving contact 56 comes into contact with the fixed contacts 46a and 46b to electrically close (the main circuit) between the fixed contact 46a and the fixed contact 46b.
When the DC voltage applied between the fixed electrode portion 35 and the movable electrode portion 36 is released, the electrostatic attractive force disappears between the branch portion 68 and the comb-shaped portion 73. Therefore, the movable electrode portion 36 is retreated in the Y-direction by the elastic restoring forces of the movable springs 37a and 37b, and the moving contact 56 is separated from the fixed contacts 46a and 46b to open (the main circuit) between the fixed contact 46a and the fixed contact 46b.
In the electrostatic relay 31, because the electrostatic actuator is driven by utilizing the electrostatic force, there is a risk that the moving contact 56 is not separated from the fixed contacts 46a and 46b even if the DC voltage applied between the fixed electrode portion 35 and the movable electrode portion 36 is released. This is because the electrodes 35 and 36 remain attracted to each other by the induction polarization or the electrostatic induction or the contacts are not separated by the adhesive force generated between the contacts even if the DC voltage applied between the fixed electrode portion 35 and the movable electrode portion 36 is released. Accordingly, in order to separate the fixed contacts 46a and 46b from the moving contact 56, the movable springs 37a and 37b having the large spring moduli are required to separate the fixed contacts 46a and 46b from the moving contact 56. However, when the spring moduli of the movable springs 37a and 37b are increased, the electrostatic actuator having the stronger electrostatic force is required to displace the movable electrode portion 36.
Therefore, in the electrostatic relay 31, besides the movable spring 37a and 37b, secondary springs 84 (second spring member) are provided in the spring supporting portions 38, and the elastic restoring forces of the secondary springs 84 are applied when the fixed contacts 46a and 46b and the moving contact 56 are separated from each other. As shown in
A length of the projection portion 85 or a distance between the leading end of the projection portion 85 and the secondary spring 84 is determined such that an operation shown in
Accordingly, when the DC voltage applied to the electrostatic actuator is released, the movable electrode portion 36 is pushed back by the elastic restoring forces of the movable springs 37a and 37b and secondary spring 84, and the movable electrode portion 36 is separated from the fixed electrode portion 35 by the strong force and returned to the original position.
The pair of movable springs 37a, the pair of movable springs 37b, the pair of secondary springs 84, and the pair of projection portions 85 are symmetrically formed in relation to the center axis parallel to the Y-direction of the movable electrode portion 36 such that the movable electrode portion 36 moves in the Y-direction without inclining the movable electrode portion 36. The pair of movable springs 37a, the pair of movable springs 37b, and the pair of secondary springs 84 has the identical spring modulus.
In the configuration of the electrostatic relay 31, the secondary springs 84 that are different from the movable springs 37a and 37b are provided to increase the spring force for returning the movable electrode portion 36, and the secondary springs 84 are not deformed until abutting on the projection portion 85. Therefore, the degree of freedom of the design is enhanced between the secondary spring 84 and the projection portion 85 to facilitate the design. In the structure shown in
On the other hand, the degree of freedom of the design is degraded, when the movable spring abuts on the operation controlling member after the movable spring is deformed like Japanese Unexamined Patent Publication No. 6-203726, or when the projection portion is provided between the movable portion and the fixed portion like Japanese Unexamined Patent Publication No. 2000-164104. This point becomes clear in consideration of a comparative example shown in
In the comparative example, as shown in
However, in the comparative example, the movable spring 37a is bent with the movement of the movable electrode portion 36, and the bent movable spring 37a abuts on the leading end of the projection 86 as shown in
Even in the comparative example, as shown by an alternate long and two short dashes line in
In the comparative example, because the position and length of the projection 86 are correlated with each other, the spring modulus of the movable spring 37a and the length of the projection 86 (or the moving distance of the movable electrode portion 36 when the spring modulus is changed) cannot independently be determined, and the design becomes complicated. On the other hand, in the first embodiment, the spring modulus of the secondary spring 84 and the moving distance of the movable electrode portion 36 in changing the spring modulus can independently be determined to facilitate the design.
(Producing Method)
A method for producing the electrostatic relay 31 will briefly be described below. A substrate shown in
Then, as shown in
The exposed region of the Si substrate 93 is dry-etched with the photoresist film 96 as an etching mask, and the fixed contact substrate 41 of the fixed contact portion 33, the moving contact substrate 51 of the moving contact portion 34, the fixed electrode substrate 61 of the fixed electrode portion 35, the movable electrode substrate 71 of the movable electrode portion 36, the movable springs 37a and 37b, the spring supporting portions 38 and 39, the secondary spring 84, and the projection portion 85 (electrostatic actuator and a switch substrate portion) are formed as shown in
After the photoresist film 96 is peeled off as shown in
(Modification)
The effect similar to that of the first embodiment can be obtained in the coupling portion 102.
(Other Modifications)
In the first and second embodiments, the movable springs 37a and 37b that support the movable electrode portion 36 are provided in the front end face and rear end face of the movable electrode portion 36. Alternatively, only one of the movable springs 37a and 37b may be provided in the front end face or rear end face of the movable electrode portion 36.
The projection portion 85 may be provided in the secondary spring 84 instead of providing the projection portion 85 in the surface that is opposite the secondary spring 84.
The positions at which the secondary spring 84 and the projection portion 85 are provided are not limited to the region between the front end face of the movable electrode portion 36 and the spring supporting portion 38, but the secondary spring 84 and the projection portion 85 may be provided at any position.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
Number | Date | Country | Kind |
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2010-055556 | Mar 2010 | JP | national |