Electricity: circuit makers and breakers – Electric switch details – Contact
Reexamination Certificate
2000-11-30
2004-09-14
Wyszomierski, George (Department: 1742)
Electricity: circuit makers and breakers
Electric switch details
Contact
C252S514000, C252S520100, C335S151000, C148S431000, C420S501000
Reexamination Certificate
active
06791045
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electric contact material useful in the fabrication of a relay for use in vehicles, the relay being highly durable against load exerted by a magnetic clutch of a vehicle air-conditioner. The invention also relates to such a relay for use in vehicles.
BACKGROUND ART
An electric contact element which makes and breaks an electric circuit is generally called an electric contact. The electric contact must allow current (signal) flow via the contact through contact between metal parts. In addition, the electric contact must completely break the circuit upon breaking of contact.
Although an electric contact per se has a simple structure, a variety of physical and chemical phenomena are known to occur at a contact surface thereof. For example, there occur adsorption, oxidation, sulfidation, and formation of organic compounds, and concomitant discharge, melting, evaporation, wear, and transfer. Such phenomena are very complex, and as a result, the phenomena have not yet been completely elucidated in studies thereon.
The occurrence of such phenomena adversely affects the function of the electric contact, in some cases leading to inhibition of the contact function (for example, the contact portions become welded together). Loss of the contact function is detrimental to the performance and service life of the electrical appliance into which such an affected electric contact is incorporated. Therefore, an electric contact is one of the important parts for determining the service life and performance of an electrical appliance.
In recent years, remarkable developments in the field of electronics and electrical engineering have made a broad range of appliances employing electric contacts available; i.e., from light electrical appliances such as apparatuses for telecommunications and electronics to heavy electrical appliances such as large-current choppers. Since the functions required vary depending on use, electric contacts having characteristics suited to various end uses have been developed. In fact, a large variety of such apparatuses are commercially available.
The existing techniques related to the types of electric contacts according to the present invention; i.e., those contacts used in relays and switches for use in vehicles, will next be described. An electric contact element which is to be used in relays and switches is called a make-and-break contact. The electric contact material for producing such a make-and-break contact is particularly required to have wear resistance and transfer resistance in order to maintain a stable make-and-break mechanism, and to have low contact resistance in order to maintain stable contact conditions.
Examples of electric contact materials conventionally employed for fabricating relays and switches for use in vehicles include Ag—Cu alloys (1-25 wt. % Cu, the balance being Ag), Ag—SnO
2
alloys (5-15 wt. % SnO
2
, the balance being Ag), and Ag—SnO
2
—In
2
O
3
alloys.
These electric contact materials may be used by themselves in unmodified form. However, usually, these materials are formed into a clad rivet contact in which two to three contact layers are laminated on a Cu or Cu alloy layer serving as a substrate layer or into a clad crossbar contact in which two to five contact layers are laminated on a Cu or Cu alloy layer serving as a substrate layer. The clad rivet contact and the clad crossbar contact are useful in the fabrication of a relay, in which an electric contact can make and break electric contact by the action of a movable iron plate which is brought into contact to a counterpart through a magnetic force produced by applying an electric current (signal) such as direct current, alternating current, or impulses to a coil in order to generate magnetic flux.
When exposed to direct-current loads in vehicles, the aforementioned conventional electric contact materials are satisfactory at a practical level in terms of wear resistance, transfer resistance, and low contact resistance. However, the following problems have been identified. Firstly, these electric contact materials do not meet demand for the smaller-sized parts of vehicles. As the functionality and performance of vehicles has increased, the number of electric parts used in vehicles has also increased, but the size of the electric parts themselves has decreased. In addition, size reduction has been performed also in consideration of cost reduction. Although there is demand for size reduction of relays and switches themselves, the aforementioned conventional electric contact materials do not lend themselves to this purpose.
Briefly, when the volume of an electric contact material decreases so as to reduce the size of a relay, the work per unit volume of the material increases greatly during the making and breaking of contact. Thus, a conventional electric contact material undergoes self-welding only after a short period of operation.
Secondly, in recent years, in addition to size reduction, there is also demand for extending the range of applications and for extending the service life of relays and switches for use in vehicles. Regarding extending the range of applications, there is demand for electric contact materials which can generally be suited for operation of a variety of loads; e.g., lamp loads where there is a flow of inrush current (head lamps and discharge lamps), resistance loads (rear defogger), and solenoid loads in which long-term arc generation occurs (magnetic clutch).
Regarding the extension of service life, there are needed electric contact materials which can be operated for a long period of time even when the electric appliance is used in a novel operational mode. For example, operation of a vehicle air-conditioner has undergone various changes. Previously, vehicle air-conditioners were usually operated only in summer. However, recently, air-conditioners have been operated throughout the year as automatically-controllable air-conditioners. Consequently, operational frequency and the operation period of relays and switches to control the air-conditioners has increased correspondingly. Thus, there is a requirement for electric contact material useful in the fabrication of make-and-break contacts to satisfy the above conditions.
Examples of relays which are currently and typically used in vehicles include an ISO (International Standardization organization) relay, a mini-ISO relay, and a micro-ISO relay. By employing Ag material such as Ag—SnO
2
or Ag—SnO
2
—In
2
O
3
to fabricate such relays, a considerable reduction in size has already been attained. However, currently employed relays used to control a magnetic clutch of a vehicle air-conditioner are not sufficiently durable. At present, simultaneous extension of both the applications and the service life of the above relays has not yet been attained.
Specifically, an open-type relay is employed as a vehicle relay for controlling a magnetic clutch which exerts an inductive load (50W) on a vehicle air-conditioner. Currently, an open-type relay has attained a durability equal to approximately 400,000 cycles of make-and-break operation. Thus, there is a further need for a relay, for use in vehicles, having a durability equal to at least 1,000,000 cycles of make-and-break operation so as to suit the relay for the aforementioned increased frequency of make-and-break operations.
The present invention has been accomplished in consideration of the foregoing. Accordingly, the invention is directed to an electric contact material useful in the fabrication of a vehicle relay of high durability against inductive load to which the relay incorporated in a magnetic clutch of a vehicle air-conditioner is exposed, and also to a relay having remarkable durability as has never been attained for use in vehicles.
DISCLOSURE OF THE INVENTION
In order to solve the aforementioned problems, the present inventors have conducted extensive studies and experiments on the composition of electric contact material for controlling a magnetic clutch (i.e., an inductive load) of a vehicle air-con
Kojima Kiyokazu
Sakaguchi Osamu
Shima Kunihiro
Yamamoto Toshiya
Combs Morillo Janelle
Rothwell Figg Ernst & Manbeck
Tanaka Kikinzoku Kogyo K.K.
Wyszomierski George
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