Sliding switch contact structure

Abstract: Disclosed is a structure of a sliding switch contact. The sliding switch contact has a movable contact and a fixed contact which are formed of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, or an Fe-Ni-Cr alloy. With such structure, a contact material is provided that is usable in a high-temperature oil contained within a transmission, an engine or a brake hydraulic system of an automotive vehicle.

Description: BACKGROUND OF THE INVENTION This invention relates to a structure of a sliding switch contact, particularly, adapted for a sliding switch that is used in high-temperature oil. Conventionally, copper alloys excellent in electric characteristics and springiness have been in general use for materials for switch contacts. There is an art disclosed, for example, by Japanese Unexamined Patent Publication No. S63-213221, wherein a copper alloy of a sheet material is employed to increase the mechanical strength for a switch contact. This prior art concerns with a technique that a spring alloy at its respective surfaces is superposed by a copper alloy to be subjected to roll working. GB 264 954 A discloses no sliding switch, but only a device for igniting and extinguishing at regular intervals the light of an electric lamp provided with a thermal interrupter. The object of this device is to avoid that the contacs weld together due to a high temperature during ignition. DE 963 346C discloses a barrel switch in which the movable contacs are mounted on the barrel and the fixed contacs are mounted in a base board. The fixed contacs are pressed against the movable contacs by means of a separate spring. Therefore the alloy of the fixed contact has no influence on the flexibility of the contact. Further there exist no problem whether there is a line or a surface contact. However, although the conventional copper switch contact possesses excellent properties as stated hereinbefore at room temperatures, there is a problem that the switch contact loses its function of contact under conditions of at temperatures of from -40 °C to 180 °C in an oil within a vehicular transmission, an engine, a brake oil-pressure system, or the like. If copper or copper alloy is used as a slide contact under the aforesaid environment, insulating compounds, such as copper oxides and sulfides, are produced over the surface thereof in a short period of time to thereby cause a problem of electrical disconnection, thus making impossible to use for contact materials. SUMMARY OF THE INVENTION It is the object of the present invention to provide a contact material that is usable in a high-temperature oil contained within a transmission, an engine or a brake hydraulic system of an automotive vehicle. The invention of claim 1 is made in order to solve the abovestated problem. In a sliding switch contact, arranged in an oil within a vehicular transmission, or the like, a structure of a sliding switch contact comprising: a movable contact (2) and a fixed contact (11) which are formed of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, or an Fe-Ni-Cr alloy, wherein said movable contact (2) is formed higher in hardness than said fixed contact (11). The invention of claim 2 comprises, in the invention of claim 1, the movable contact that is formed of a stainless steel and the fixed contact is of an Fe-Ni alloy. The invention of claim 3 comprises, in the invention of claim 1, the movable contact that is formed of a stainless steel and the fixed contact is of an Fe-Ni-Co alloy. The invention of claim 4 comprises, in the claim 1, the movable contact that is formed of a stainless steel and the fixed contact is of an Fe-Ni-Cr alloy. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view showing an embodiment of the present invention; Fig. 2 is an exploded perspective view showing a shape of a fixed contact prior to separating into contact portions and terminals, according to the embodiment of the present invention; Fig. 3 is a perspective view of a switch showing the embodiment of the present invention; Fig. 4 is an exploded perspective view of the switch showing the embodiment of the present invention; and Fig. 5 is a graph showing data according to the embodiment of the present invention, wherein the relationship between variation in voltage drop and time is shown where the fixed contact and the movable contact is immersed in a transmission oil at 150 °C. PREFERRED EMBODIMENT OF THE INVENTION Now explanations will be made in detail on an embodiment of the present invention with reference to Fig. 1. In Fig. 1, there is illustrated at 1 a base board which is insert-formed with a fixed contact 11 and formed of a heat-resistive resin. The fixed contact 11 is formed of an Fe-based alloy that is lower in hardness than a movable contact 2. The Fe-based alloy for the fixed contact 11 is, for example, of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, an Fe-Ni-Cr alloy, or the like. Note that there is no especial limitation in the shape of the fixed contact 11. The movable contact 2 is a sliding switch contact piece which is formed of an Fe alloy higher in hardness than the fixed contact 11 and arranged for slide movement in directions of the arrows X and Y. The movable contact 2 is formed of an Fe alloy, such as a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, an Fe-Ni-Cr alloy, or the like. For example, where the movable contact 2 is formed of a stainless steel, the fixed contact 11 is formed, for example, of an Fe-Ni alloy. Meanwhile, where the movable contact 2 is formed of a stainless steel, the fixed contact 11 is formed, for example, of an Fe-Ni-Co alloy. Where the movable contact 2 is formed of a stainless steel, the fixed contact 11 is formed, for example, of an Fe-Ni-Cr alloy. The embodiment of the present invention is structured as described above, and the operation thereof will now be explained. The movable contact 2 and the fixed contact 11 are of an Fe-based alloy, e.g. of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, an Fe-Ni-Cr alloy, or the like. The Fe-based alloy is heat-resistant and excellent in chemical stability as compared to Cu or Cu alloys. The Fe-base alloy will not produce insulating compounds even ehen placed within a high-temperature oil, so that it can keep a function as a manually-operated contact over a long term. The movable contact 2 is of an Fe alloy increased in hardness higher than the fixed contact 11. Due to this, the fixed contact 11 is cut away by a constant amount as the number of slide movements increases, providing a stable cut surface. The movable contact 2, in turns, has increased electrical stability during its sliding motion. The movable contact 2 formed of a stainless steel has a high property of a compound film (passivity) formed over the surface thereof, thus being chemically stable. If the passivity film at the surface of the movable contact 2 is cut away, a new film is again formed, keeping resistance to an outside environment. The fixed contact 11 formed of an Fe-Ni alloy contains a large amount of Ni, and accordingly is chemically stable. The fixed contact 11 has no difference in composition of material between the surface and the internal thereof so that the contact 11 will not deteriorate in chemical stability despite it is cut by the sliding of the movable contact 2. That is, the movable contact 2 and the fixed contact 11 are best suited for contacts for a sliding switch that is used in a high-temperature oil within a vehicular transmission, an engine, a brake hydraulic system, or the like. Example Explanations will now be made in detail for an example according to the present invention with reference to Fig. 2, Fig. 3, Fig. 4 and Fig. 5. The example is on a sliding switch which is used in a state of being submerged in an oil of an automatic transmission for automotive vehicles. In Fig. 2, 1 is a base board formed of a synthetic resin, so that it is heat-resisting and oil-resisting to withstand in use where it is submerged in a high-temperature oil in an automatic transmission for automotive vehicles. The base board 1 is insert-formed with a fixed contact 11 and a terminal 111 in connection to the fixed contact 11. The base board 1, as shown in Fig. 4, is provided at a back side thereof with rows of contact portions 112 of the fixed contact 11 over which the movable contact 2 slides. The base board 1 has a wall-shaped projections (not shown) formed along the contact portion 112 and between the contact portions 112 juxtaposed, e.g. in five rows. The projections has dual functions to enhance insulating property as well as guide the projections 31 of a movable board 3 to allow the movable contacts 21 to move straightly. The base board 1 has a connector 13 formed in one body therewith, so that the terminal 111 in electrical connection to the fixed contact 11 projects toward the inside of the connector 13. The base board 1 is provided with clinch portions 14 at several points on an outer periphery thereof. The clinch portions 14 are portions over which clinch pieces 53 of a frame member 5 are respectively clinched. The fixed contact 11 and the terminal 111 are formed, as stated above, of an Fe-based alloy, e.g. stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, an Fe-Ni-Cr alloy or the like. The fixed contact 11 and the terminal 111 are formed by dividing one metal sheet into two, as shown in Fig. 2, each of which is further press-worked in order into a plurality of sheets as shown by a broken line in Fig. 4. The movable contact 2 is a sliding piece formed, as stated above, of an Fe-based alloy, e.g. a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, an Fe-Ni-Cr alloy, or the like. The movable contact 2 is worked by press-blanking and bending from one metal sheet. The movable contact 2 has five sets of contact pieces 21, chatter-preventing pieces 22, 23, 24, 25, and leadframes 26, 27. The movable contact 2, as shown 4, is a contact sheet for the contact switch that has a plural pairs of the contact pieces 21 alternately projected in different directions from the left and right of the leadframes 26, 27 formed generally in a quadrilateral shape. The movable contact 2 is held by the movable board 3 by inserting its leadframes 26, 27 into gaps 37 formed at an underside of L-shaped protrusions 31 projected at opposite edges of the movable board 3. The contact pieces 21 are each formed by a pair of adjacent tongue pieces so that the number thereof is the same as that of the contact portions 112 of the fixed contact 11. The contact piece 21 is curved toward the fixed contact 11 to have elasticity. The chatter-preventing pieces 22, 23, 24, 25 are provided at ends of the leadframe 26 correspondingly to step portions 32, 33 and engaging portions 34, 35, so that the movable contact 2 is assembled onto the movable board in a one-touch manner by engaging the chattering-preventing pieces with the step portions 32, 33 and the engaging portions 34, 35. The movable board 3 is formed of a synthetic resin to have the protrusions 31 for wiping over the surface of the fixed contact 11, the gaps 37 extending in a direction rectangular to the direction of slide movement thereof so as to receive therein the movable contact 2 from the rectangular direction, the step portions 32, 33 formed on an extension of the gaps 37, and the engaging portions 34, 35 formed in a valley-like form in section. The movable board 3 further insert-formed with a metallic pin 36 for engagement with an operating member 4. Now explanations will be made on the procedure for assembling the movable contact 2 onto the movable board in a one-touch manner. First, the leadframes 26, 27 are inserted into the gaps 37, 38 from the side of the chatter-preventing pieces 23, 24, as shown in Fig. 4. When inserting by a certain amount, the chatter-preventing piece 23 comes into abuttment against the step portion 33 to block the movable contact 2 from moving further forwardly. At this time, the chatter-preventing piece 22, positioned at the opposite side to the chatter-preventing piece 23, gets over the step portion 32 to be elastically fitted with the movable board 3. Thus, the movable contact 2 is prevented from chattering in the rectangular direction. On the other hand, the chatter-preventing pieces 24, 25 are press-contacted with the engaging portions 34, 35 of the movable board 3. Thus, the movable contact 2 is prevented from chattering in the sliding direction. The operating member 4 has a connecting portion 41 for connection to an manual valve (not shown) of the automatic transmission, an inserting portion 42 over which a guide block 6 is inserted, and an engaging hole 43 with which a pin 36 of the movable board 3 is engaged. The engaging hole 43 is in a hole shape that is formed long in a rectangular direction relative to the direction of movement of the movable board 3. A frame 5 is a part that has been worked by pressing from a metal plate, and has an elongate hole 51 through which the pin 36 of the movable board 3 is inserted, holes 52 provided corresponding to holes 72 of a bracket 7, and clinch pieces 53 for being clinched to the clinch portion 14 of the board 1. The movable board 3 is accommodated within a space defined by the frame 5 and the board 1. The elongate hole 51 has its width dimension somewhat greater than the diameter of the pin 36. A guide block 6 is a part that is interposed between the operating member 4 and the base board 1 so that the operating member 4 is guided along a rail 15 provided on the board 1. The guide block 6 has insertion grooves 61, 62 in which inserting portions 42 are inserted, and a recess 63 in which the rail 15 is inserted. The bracket 7 has mounting holes for mount on a case of the automatic transmission, and holes 72 for attaching to the frame 5, so that the bracket 7 and the frame 5 are fixed by tightening with screws (not shown) through the holes 72 and the holes 52. The one embodiment of the present invention is structured as above. Now explanations will be further made on materials for the movable contact 2 and the fixed contact 11. The movable contact 2 and the fixed contact 11 are formed of an Fe alloy, e.g. of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, an Fe-Ni-Cr alloy, or the like. The movable contact 2 is formed high in hardness than the fixed contact 11. For example, Fig. 5 is a graph showing the comparison in environment-resisting characteristics between the fixed contact 11and the movable contact 2 according to the present invention and the conventional usual fixed contact and movable. The abscissa represent hours [H], while the ordinate denotes voltage drops [mV]. A is data on voltage drops measured by flowing a 800-mA electric current through the fixed contact 11 and the movable contact 2 which are respectively formed of a 42Ni-Fe alloy material and a SUS301 material according to the present invention to be submerged in a transmission oil at 150 °C. B is data on voltage drops measured by flowing a 800-mA electric current through a fixed contact and a movable contact which are respectively formed of conventionally usual oxidation-free and phosphor bronze to be submerged in a transmission oil at 150 °C. As shown in Fig. 5, the movable contact 2 and the fixed contact 11 are heat-resisting and oil-resiting and hence excellent in environment-resisting characteristics as compared to the conventional fixed contact and the movable contact of conventional copper and copper-based alloy. Table 1, shown below, is a comparison table showing data, as to spring property and chemical stability, concerning coventional copper, copper-based alloys, SUS alloys, and Fe-Ni alloys. Item Material Electric resistance µΩ/cm Young's modulus P/mm 2 Spring characteristic Chemical characteristic Oxygen-free copper 2 11800 × × Phosphor copper 7 11000 o ○ × Beryllium copper 7 12500 o ○ × SUS301 71 19700 ○ o ○ SUS304 72 19300 ○ o ○ SUS405 60 20000 Δ o ○ SUS403 57 20000 Δ o ○ 42NI-Fe 63 13500 × ○ 52Ni-16Co-Fe 43 - × ○ 29Ni-16Cr-Fe 48 14000 × ○ 42Ni-06Cr-Fe 95 - × ○ In the material column of Table 1, the numeral described on the left of a chemical symbol Ni, Co or Cr denotes the ratio (weight %) of alloy. The spring property represents usable or nonusable as a spring material. In the material column of Table 1, SUS 301 and SUS304 are of austenitic stainless steel. SUS405 is of a ferritic stainless steel. SUS403 is of a martensitic stainless steel. 42Ni-Fe and 52Ni-Fe are nickel steels as electronic materials. 29Ni-16Co-Fe is of a nickel-constantan steel as an electronic material. 42-Ni-06Cr-Fe is a nickel-chromium steel as an electronic material. In the spring characteristic column of Table 1, o ○ represents that the material is especially excellent as a spring material and a metal in common use. ○ denotes a metal that is commonly used as a spring material. Δ is a metal not commonly used as a spring material, which is possible to use but requires devising upon usage. X represent a metal impossible to use as a spring material, and is not commonly used. In the chemical stability column of Table 1, chemical stability for the metal is shown where it has been immersed in a transmission oil at a temperature of 150 °C. In the chemical stability column of Table 1, o ○ represents a metal that is free of occurrence of insulating compounds harmful to switch contacts, and hence particularly excellent. ○ is a metal that produces somewhat insulating compounds harmful to switch contacts, but excellent without problem in use. Δ denotes a metal possible to use for switch contacts, but requires devising upon usage. X is a metal that produces insulating compounds such as sulfides or the like harmful to switch contacts. As shown in Table 1, the conventional copper and the copper-based alloys are poor in chemical stability and cannot be used in high-temperature oils. It is revealed that the stainless steels are excellent in chemical stability, with spring characteristic. In particular, it is understood that SUS301 and SUS304 are excellent in chemical stability and spring characteristic, and best suited as a material for the movable contact. Meanwhile, the nickel-based alloy steels are best suited for the fixed contact 11. The present invention structured as described above provides effects as given below. The invention of claim 1 is characterized by, in a sliding switch contact, a structure of a sliding switch contact comprising: a movable contact and a fixed contact which are formed of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, or an Fe-Ni-Cr alloy. It is therefore possible to provide, at a low cost, a structure of a switch contact for sliding switches which is best suited for use in a high-temperature oil. The invention of claim 2 comprises, in the invention of claim 1, the movable contact that is formed higher in hardness than the fixed contact. Therefore, the fixed contact is cut away by an amount proportional to the number of slides of the movable contact increases. The inventions of claim 3 to claim 5 comprises, in the invention of claim 1 or claim 2, the movable contact 2 that is formed of a stainless steel and the fixed contact 11 is of an Fe-Ni alloy, an Fe-Ni-Co alloy or an Fe-Ni-Cr alloy. It is therefore possible to provide a structure of a movable contact and a fixed contact for a sliding switch that is usable in a high-temperature oil in an automotive vehicle transmission, engine, brake hydraulic system, or the like.

Claims: A sliding switch contact, arranged in an oil within a vehicular transmission, or the like, comprising: a movable contact (2) and a fixed contact (11) which are formed of a stainless steel, an Fe-Ni alloy, an Fe-Ni-Co alloy, or an Fe-Ni-Cr alloy, wherein said movable contact (2) is formed higher in hardness than said fixed contact (11). A sliding switch contact according to claim 1, wherein said movable contact (2) is formed of a stainless steel and said fixed contact (11) is of an Fe-Ni alloy. A sliding switch contact according to claim 1, wherein said movable contact (2) is formed of a stainless steel and said fixed contact is of an Fe-Ni-Co alloy. A sliding switch contact according to claim 1, wherein said movable contact (2) is formed of a stainless steel and said fixed contact is of an Fe-Ni-Cr alloy.

Inventors: SATOU SHUNICHI, SATOU, SHUNICHI
Applicants: NILES PARTS CO LTD, NILES PARTS CO., LTD.
Application year: 1998
Main classification: H01H1
IPC codes: H01H1, H01H15